Data Migrations (DM): The SQL Server Perspective (Licensing Costs and Edition Choices)

Data Migration Series

A Data Migration (DM) moves all or a subset of the data available from one or more system(s) into other system(s). For this purpose, especially in ERP Implementations, one can use a SQL Server as intermediate layer, where SSIS can be used for the data extraction and exporting, SSRS for reporting the errors, while the database engine for the heavy processing. Master Data and Data Quality Services can be used as well in certain scenarios. Therefore, SQL Server allows by design to address the various challenges related to a DM. At high level the architecture can be depicted as follows:

Data Migration Architecture

Once the decision to go with SQL Server for the DM layer is made, one needs to define which edition to use. If the DM doesn't have special requirements, one can use for it an available SQL Server instance, as long as the cumulated workloads don't create major issues. Therefore, in the past I used existing licensed versions of SQL Server to build solutions for DMs in ERP implementations, though I evaluated in each project whether it's possible to reduce the costs and remain compliant with the license requirements. 

Of course, there's always the alternative of using SQL Server Express which supports databases with a maximum of 10 GB, which should be enough for most of DMs, though it has also further limitations (see [2]). There are also ways of moving around existing limitations, like splitting the logic across multiple databases. 

Then there's the SQL Server Developer edition, which involves no license costs, has the full SQL Server functionality available, and can be used to build and test applications. In a recent post [1], Bob Ward, principal architect at Microsoft made several clarifications on the licenses for the Developer edition, which is "licensed for development, test, and demonstration purposes only" and "may not be used in a production environment”. Bob Ward makes the following clarifications:
(1) "Production environments include any system that is accessed by end-users for anything more than acceptance testing, environments that connects to production systems (such as Linked servers), disaster recovery or backups of production systems, and environments that are 'rotated' into production at any point in time." [1]
(2) One "cannot use Developer edition to build test data and move that same data into production" [1].
(3) One can "restore a production set of data backup for testing purposes" [1].

There are two-three impediments for using the Developer edition completely for a DM. The first, at least during Go Live and UAT, one needs to work with data coming directly from the various production environments. Secondly, the data generated by the solution are used primarily for UAT and in a second step for Production, which seems to be against the rule (2), or at least it's a grey area (which might be overlooked by Microsoft). Thirdly, some data from the production environment might need to be imported back into the DM layer for validation or enhancing the entities with data generated in the target systems. 

In what concerns the first issue, the DM solution can always point to the test environments used as source, following that during UAT to copy the databases from production into the test environments. This might be anyway necessary for other purposes. Otherwise, the effort might be considerable and not working in the last phases with the data timeliness might raise other concerns. 

The second issue is a matter of interpretation. The UAT phase makes sure that the data generated by the DM solution respects the criteria for Go Live. If there are no issues, the same data can be used for Go-Live. If for this is required another licensed edition, then an environment can be built only for UAT and Go Live, project phases which usually span over a couple of weeks, unless multiple migrations need to be performed at different time intervals. If the environments are in the cloud, probably the instances can be turned on and off on a as-needed basis. 

One can plan for different environments between Production and Development and the environments can be on the same SQL Server as distinct databases, respectively use the Developer edition for Development, and use a different licensed edition for UAT and Production. This approach involves additional overhead in synchronizing the logic between environments. Conversely, in the case of the DM layer, the same environment can be used from beginning to the end, while the code should/must be backed-up periodically. For multiple migrations based on the same data, one should archive the data after each migration or important phase. 

For the scenarios in which after migration the data are copied back to the DM solution, it's enough to have these steps performed against the UAT target system(s). This should work as long there are no differences in configuration between UAT and Production. There are however exceptions, e.g. data generated by the target systems, for which the values between Prod and UAT are different. At least in Dynamics 365 one can attempt to generate the values in the DM layer and import them as they are into the target system. It worked for many scenarios, though there can be exceptions here as well. 

A more complex scenario is when data from the DM layer needs to be exported to Data Warehouses or similar solutions that can be considered as Production systems. Here a licensed edition seems to be mandatory. For other scenarios in which Master Data and/or Data Quality Services are needed, there's only the option to use the Enterprise or Developer editions.

To summarize, to reduce the overall costs for the DM, consider using an existing licensed SQL Server instance for building the solution. If separates environments need to be built, the Express edition might have some limitations though it can prove to be a viable solutions in many cases. Otherwise, consider the above workarounds for using the Developer edition, including the scenario in which distinct environments are used for Production and Development. 

Resources:
[1] Microsoft Data Platform (2024) How SQL developers can maximize savings, by Bob Ward (link)
[2] Microsoft Learn (2024) Editions and supported features of SQL Server 2022 (link)
[3] Microsoft Learn (2023) Master Data Services and Data Quality Services Features Support (link)

ERP Implementations: Introducing an Upfront Proof-of-Concept Setup

 

The standard phases of an ERP implementation are mandatory and inflexible as there seems to exist a imposed succession of the phases rooted in customer’s need of having an upfront cost estimate for the project. Moreover, the concept-based approach reflected in the creation of a set of Functional Design Documents (FDDs), even if it’s supposed to increase an implementation’s accuracy, it brings considerable challenges and an effort volume that could be spent in other areas. E.g., having a proof-of-concept setup subproject early in the project seems to bring more benefits.

Usually, before or during the requirements gathering phase the functional consultants together with the key users look at the legacy system(s) and data, questions are asked on both sides, and the findings are hopefully documented, though the outputs are high-level ideas or process design sketches. The sessions are abstract, and besides diagrams there’s no feedback mechanism to make sure that the parties understood customer’s processes and data structures, respectively that the key users understood what the future system is supposed to deliver. Some projects consider the building of 'AS-IS' diagrams and/or user stories during this phase, though their impact on project’s outcomes is questionable.

Why not include in this phase also hand-on training sessions for the key users during which a system is set up based on the available information? For example, one can start with an existing shell of the system reflecting standard parameters used in the industry where the customer works. Starting from this shell the key users and consultants go through the various processes and business scenarios, change parameters, add master data manually, sketch how the process could look like, respectively understand the gaps from expectations, or maybe how the process can be changed to avoid customizations. That’s more effective than discussing over and over the data structures and processes!

Of course, this seems to increase exploratory phase's complexity, though the increase is apparent. Allowing key users to understand how the target system works has the potential of simplifying project's planning and execution. Besides reaching a common understanding of the functionality, the key users can better evaluate whether the target system satisfies the high-level requirements, respectively better perform the various activities - requirements’ definition, reviews and user acceptance testing benefiting altogether. Moreover, they can train and involve other users earlier.

For this to work there are several assumptions. First, that the functional consultants know the target system(s), which is not necessarily needed in other approaches where a person (e.g. business analyst) who can understand how a system works and can document processes is enough. Second, the key users must have a good understanding of the legacy systems. Third, the shell should reflect the business needs as much as possible. Fourth, the necessary financial resources need to be made available upfront. Fifth, the business commitment must be there, and with this the key users should focus only on the project.

However, the most important aspect is that the parties involved need to buy and support the idea! The FDDs bring a safety net and make sense for both parties, the setup being performed only after the signoff. On the other hand, because of the considerable number of iterations FDDs involve high costs. Performing first the setup as described above and writing later the FDDs, if still needed, should improve FDDs’ quality, and require fewer iterations.

This approach allows an important volume of work to be done upfront, and even if further effort is needed for customizations and testing, a lower level of coordination is needed later, reducing thus the complexity of the planning and of the overall project.

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ERP Implementations: Simplifying the Implementation Project

 

ERPimplementations are complex projects and a way to manage their complexity is to attempt reducing their complexity (instead of answering to complexity by complexity). A project implementation’s methodology is probably the most important area that allows project’s simplification, though none of the available methodologies seems to work well with such projects.

The point that differentiates the various methodologies is solution’s conceptualization. In general, the expectation is to have a set of functional design documents (FDDs) that describe how the system operates and that can be used for programming the customizations, if any. The customer must review and sign-off the FDDs before the setup is done, respectively the development starts. Moreover, given the dependencies between documents, they often need to be signed off together.

Unfortunately, FDDs reflect the degree of understanding of the target system and business requirements, gaps that can prove to be a challenge for the parties involved, requiring many iterations until they are brought to the expected quality level. The higher the accuracy considered; the more iterations are needed. FDDs tend to consume a considerable percent of the available financial resources, in extremis the whole budget being exhausted just for 'printed paper'. Moreover, the key users see late in the project the working functionality.

In agile methodologies, FDDs are replaced by user stories, and, if still needed, can be written as part of the sprints or later. Unfortunately, agile methodologies have their own challenges and constraints in ERP implementations. As functionality is explored, understood, and negotiated with the customer during the implementation, it’s seldom possible to provide a realistic cost estimation upfront. Given that most ERP implementations exceed their budget, starting a journey without having an idea how much the project costs seems to be a prohibitive approach for many customers. Moreover, the negotiations have the character of Change Requests, which can easily become a bottleneck for the project.

On the other hand, agile methodologies involve the customer earlier and the development could start earlier as well. The earlier the customer is involved, the earlier the key users understand how the system works, and thus they can be more efficient in performing their activities, respectively in identifying the gaps in understanding, trapping functional issues early in the process, at least in theory. Some projects address this need by having the key user trained, though the training environment usually has a different setup and data than needed by the customer. Wouldn’t be a good idea to have the key users trained in an environment that reflects to a higher or lower degree the customer’s data and setup requirements?

In theory the setup for such an environment can be done upfront based on one standard configuration frequently met in customer’s industry. With this the functional consultants can start to configure the system together with the key users exploring the data and setup existing in the legacy system(s). This would allow increasing on both sides the depth of understanding and has the potential of speeding up the implementation. This can be started in the early phases, during the time in which the requirements are gathered. Ideally, a basic setup can exist already when the requirements are signed off. It’s true that this approach would mean a higher investment upfront, though the impact could be considerable. Excepting Data Migration and customizations the customer already has a good basis for Go-Live.

Of course, there can be further challenges, though the customer can make thus sure that the financial resources are well spent – having a usable system, respectively a good system understanding outweighs by far the extreme alternative of having high-quality unimplemented FDDs!

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ERP Implementations: It’s a Matter of Complexity

 

There are many factors to blame for implementation process’ inefficiency, however many of the factors can be associated with the complexity of the project itself, respectively of the application(s) involved. The problem of complexity can be addressed by either answering to complexity with complexity, building a complex team to handle the tasks, which is seldom feasible even if many organizations do it, respectively by simplifying the implementation process and/or the application.

In what concerns the project, the complexity starts with requirement’s elicitation, the iterative transformations they suffer until the final functional requirements document is finalized, their evaluation and mapping to features, respectively gap’s identification. It’s a complex task because it involves understanding the business as well the functionality available in the target system(s). Then comes the effort estimation, which, as the name suggests, is just a guess based on available historical numbers and/or experts’ opinion. High-level requirements are easier to manage than low-level requirements, however they allow for more gaps in understanding. The more detailed the specifications, the more they should help in the estimation process, though that’s the theory. A considerable number of factors can impact the process.

Even if there are standard activities in the implementation process, the number of resources involved from the customer as well from the partner(s) side makes the whole planning process a nightmare for any Project Manager, no matter how experienced he/she is.

Ideally, each member of the team should behave like a trooper, knowing by instinct when and what needs to be done, which are the expectations, etc. This might be close to expectation on the partner side as the resources more likely participated in similar projects, though there’s always a mix between levels of expertise, resources migrating between projects. Unfortunately, that’s seldom (never) the case on the customer side as the gap between reality and expectation is considerable.

Each team member requires a minimum of information/knowledge so he/she can perform the activities assigned. Moreover, the volume of coordination and cooperation is considerably higher than in other projects, complexity that increases with organization’s size and is inverse proportional with organization’s maturity in managing projects and implementation-related activities. There’s thus a minimum of initial communication needed, and furthermore communication needs to occur between the parties involved. Moreover, the higher the lack of cohesion between the parties, the higher the need for communication and this applies especially when multiple organizations are involved in the project.

The triple constraint of Project Management between scope, cost, and time, respectively on quality has an important impact on the project. Resources need to be available when the project needs them and, especially on the partner side, only when they are needed. The implementation project to be feasible for the partner, its resources must work on several projects in parallel or the timing must be perfect, that no waiting times are involved, respectively the effort is concentrated only when needed. Such precision is possible maybe at project’s beginning, though the further the project evolves, the more challenging becomes the coordination of resources. Similar considerations apply to the customer as well.

Thus, a more realistic expectation is to have resources available only at certain points in time, and the resources should be capable of juggling between projects, respectively between project and other activities. Prioritizing is a must, and sometimes the operations or other projects have higher priority. When the time is not available, resources need to compromise by reducing the level of quality.

On the other side, it would be great if most of the effort could be concentrated at the beginning of the project, the later interactions being minimal.  

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ERP Implementations: The Implementation Process Seems to be Broken

 

Participating in several ERP implementations, one has the expectation that things will change for the better when moving from one implementation to another. Things change positively in certain areas as experience is integrated, though on average the overall performance seems to be the same. Thus, one may wonder, how can this happen? Of course, there are so many explanations - what went wrong, what could have been done better, and the list is usually quite big. However, the history repeats in the next implementation. Something seems to be broken, or maybe this is the way implementations should work, though I doubt this!

An ERP implementation starts with a need and the customer usually has an idea of what the respective need is about. It might even have a set of high-level or even low-level requirements, which should be the case when starting on such a journey. Then the customer selects an implementation partner, event followed by a period of discovery in which the partner learns more about the business including the overall infrastructure, business processes, data and people. Once the requirements are available, the partner can evaluate them to identify the deviations from the standard functionality available and that translate into customizations, sketch solutions, respectively make a first estimate of the costs and resources needed.

Of course, there can be multiple iterations of the process in which the requirements are reviewed, reevaluated, justified, prioritized by all parties and a common understanding, respectively an agreement on the scope and expectations is reached. In the process some requirements are dropped, others are modified or postponed for a later phase or later phases. The whole process can take a few months, though it’s mandatory for creating a workable estimate used as basis for the statement of work and the overall contract.

In parallel the parties can also work on a project plan and agree upon a project methodology, following that once the legal paperwork is signed, resources to be allocated to the project. A common practice is then for the functional consultants to generate based on the requirements a set of documents - functional design documents (FDD), process diagrams - that should be used as basis for the setup, for programming the customizations and User acceptance testing (UAT). Of course, the documents need to be reviewed by the business, gaps or misunderstandings mitigated, and this takes several iterations until the business can sign-off on the respective documents. It’s the point where the setup and programming can start, usually half a year, or even a year or more after the initial steps.

Depending on the scope, in the best-case scenario the setup will take one to two months, at least until having a system ready for UAT with business data as needed for Go-Live. The agreed customizations can translate in further months and effort not only for programming, but also for testing, reviewing and further mitigations. This would be the time when many of the key users see for the first time a working version of the system, which frankly might be too late. Of course, they read and reread the FDDs, though until this point everything was very abstract and no matter how good such documents were written, they can’t replace the hand-on experience with working with the system, discovering the functionality, understanding how it works.

In the best-case scenario, the key-users are satisfied with the results and the UAT, respectively Go-Live can go on as planned, however the expectations for first time right are seldom (never) met. Further iterations and delays are then involved. Overall, the process doesn’t seem to be efficient!

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ERP Implementations: It’s all about Partnership II

When starting an ERP implementation project an organization needs to fill the existing knowledge gaps in respect to whatever it takes to achieve the goals associated with the respective project. Therefore, it makes sense to work with a implementer that can help cover the gaps directly or indirectly. Moreover, it makes sense to establish a long-term relationship that would allow to harness ERP system’s capabilities after project’s end, increase the ROI and, why not, find other areas of cooperation. It’s in theory what a partner does, and a strategic technology partnership is about – providing any kind of technological expertise the customer doesn't have in-house. 

Unfortunately, from being a ‘service provider’ to becoming a ‘partner’ is a challenging road for many organizations, especially when this type of relationship is not understood and managed accordingly. Partnership’s management may resume in defining common goals, principles, values and processes, establishing a communication strategy and a common understanding of the challenges and the steps ahead, providing visibility into the cost estimates, billing, resources’ availability and utilization. Addressing these aspects would offer a framework on which the partnerships can nourish. Without considering these topics, the implementer remains just a 'service provider', no matter of the names used to characterize the relationship. 

Now, the use of the word ‘partner’ would make someone think that only one partner is considered, typically a big to middle-sized organization that would have this kind of resources. The main reason behind this reasoning is that the number of functional areas and volume of skillset required for filling the requirements of an implementation are high compared with other projects, the resources needing to be available on-demand without affecting the other constraints: costs, quality, time. This can be challenging, therefore can be met scenarios in which two or more external organizations are involved in the partnership, ideally organizations that complement each other. 

It is common in ERP implementations to appeal also to individual consultants for specific areas or the whole project. The principles and values of a partnership, as well the framework behind, can be applied to individual consultants as well. Independently of resources’ provenience more important is the partnership ‘mindset’ - being together in the same boat, working together on a shared and understood strategy, with clear goals and objectives.

Moreover, the people participating in the project must have a ‘partner's mindset’ as well. Without this, the project will likely get different impulses in the wrong direction(s), as a group’s interests will take priority over the ones of the organization. Ideally, this mindset should extend to the whole organization as topics like Data Quality and Process Improvement must be an organization’s effort, deep imprinted in organization’s culture.

More like ever, it’s important for the business to see and treat the IT department as a ‘partner’ and not as a ‘service provider’ by providing the needed level of transparency in requirements, issues, practices and processes, by treating the IT department as equal party in the decision-making and addressing its current and future strategical requirements. Ideally, this partnership should happen long before the implementation starts, given that it takes time for mentalities and practices to change, for knowledge to be acquired and used appropriately. 

Building a partnership takes time, effort and strategic thinking, this on top of the actual implementation, increasing thus the overall complexity, at least at the beginning. Does it pay off? Like in a marriage, it’s useful to have somebody you can trust, who knows you, whom you can rely upon, and talk with to find solutions. However, only time will tell whether such expectations are met and kept till the end. 

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Strategic Management: The Impact of New Technologies I (A Nail Keeps the Shoe)

Probably one of the most misunderstood aspects for businesses is the implications the adoption of a new technology have in terms of effort, resources, infrastructure and changes, these considered before, during and post-implementation. Unfortunately, getting a new BI tool or ERP system is not like buying a new car, even if customers’ desires might revolve around such expectations. After all, the customer has been using a BI tool or ERP system for ages, the employees should be able to do the same job as before, right?

In theory adopting a new system is supposed to bring organizations a competitive advantage or other advantages - allow them reduce costs, improve their agility and decision-making, etc. However, the advantages brought by new technologies remain only as potentials unless their capabilities aren’t harnessed adequately. Keeping the car metaphor, besides looking good in the car, having a better mileage or having x years of service, buying a highly technologically-advanced car more likely will bring little benefit for the customer unless he needs, is able to use, and uses the additional features.

Both types of systems mentioned above can be quite expensive when considering the benefits associated with them. Therefore, looking at the features and the further requirements is critical for better understanding the fit. In the end one doesn’t need to buy a luxurious or sport car when one just needs to move from point A to B on small distances. In some occasions a bike or a rental car might do as well. Moreover, besides the acquisition costs, the additional features might involve considerable investments as long the warranty is broken and something needs to be fixed. In extremis, after a few years it might be even cheaper to 'replace' the whole car. Unfortunately, one can’t change systems yet, as if they were cars.

Implementing a new BI tool can take a few weeks if it doesn’t involve architecture changes within the BI infrastructure. Otherwise replacing a BI infrastructure can take from months to one year until having a stable environment. Similarly, an ERP solution can take from six months to years to implement and typically this has impact also on the BI infrastructure. Moreover, the implementation is only the top of the iceberg as further optimizations and changes are needed. It can take even more time until seeing the benefits for the investment.

A new technology can easily have the impact of dominoes within the organization. This effect is best reflected in sayings of the type: 'the wise tell us that a nail keeps a shoe, a shoe a horse, a horse a man, a man a castle, that can fight' and which reflect the impact tools technologies have within organizations when regarded within the broader context. Buying a big car, might involve extending the garage or eventually buying a new house with a bigger garage, or of replacing other devices just for the sake of using them with the new car. Even if not always perceptible, such dependencies are there, and even if the further investments might be acceptable and make sense, the implications can be a bigger shoe that one can wear. Then, the reversed saying can hold: 'for want of a nail, the shoe was lost; for want of a shoe the horse was lost; and for want of a horse the rider was lost'.

For IT technologies the impact is multidimensional as the change of a technology has impact on the IT infrastructure, on the processes associated with them, on the resources required and their skillset, respectively on the various types of flows (data, information, knowledge, materials, money).

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Data Migrations (DM): Conceptualization VII (Data Import Layer)

Data Migrations Series

The data requirements for the Data Migration (DM) and Data Quality (DQ) are driven by the processes implemented in the target system(s). Therefore, a good knowledge of these requirements can decrease the effort needed for these two subprojects considerably. The needed knowledge basis starts with the entities and their attributes, the dependencies existing between them and the various rules that apply, and ends with the parametrization requirements, respectively the architecture(s) that can be used to import the data.

The DM process starts with defining the entities in scope and their attributes, respectively identifying the corresponding entities and attributes from the legacy systems. The attributes not having a correspondent in the legacy system need to be provided by the business and integrated in the DM logic. In addition, it’s needed to consider also the attributes needed by the business and not available in the target system, some of them more likely available in the legacy systems. For such attributes is needed either to misuse an attribute from the target or to extend the target system.

For each entity is created a data mapping that basically documents the data transformations needed for migrating the data. In the process is needed to consider also attributes’ data types, the (standard) formatting, their domain of definition, as well the various rules that apply. Their implementation belongs into the DM layer from which the data are exported in a standard format as needed by the target system.

Exporting the data from the DM layer directly into the target system’s tables has in theory the lowest overhead even if the rejected records are difficult to track, the rejections resulting only from records’ ‘validation against database’s schema. For this approach to work, one must have a good knowledge of the database schema and of the business rules implemented into the target system.

To solve the issue with errors’ logging, systems have a further layer on top of the database model, which also allow running data validation against target system’s business rules. Modern import frameworks allow loading the data via a set of standard files with a predefined structure. The data can be thus imported manually or via load jobs into the system a log with the issues being generated in the process. Some frameworks allow even the manual editing of failed records, respectively to import the data. Unfortunately, calling the layer from the DM layer is not possible from a database, though this would bring seldom a benefit. Some third-party tools attempt to improve the import functionality by calling the target system’s import layer.

The import files must be generated from the DM layer in the required structure with the appropriate formatting. The challenge however resides in identifying all the attributes that should make scope of the load. It’s an iterative process which sometimes is backed by try-and-error heuristics. Unless target system’s validation rules are known beforehand, the rules need to be discovered in this process, which can prove time-consuming. The discoveries need to be integrated also in the DM and from here results the big number of changes that need to be performed.

Given the dependencies existing between entities the files need to be generated and loaded in a predefined order. These dependencies are reflected also in the data processing and the validation rules considered in the DM layer.

A quality checkpoint can be implemented between the export from the DM layer and import to enforce the four-eyes principle. It’s normally the last opportunity for trapping the eventual issues. A further quality check is performed after import by validating on whether the data were imported as expected.

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Data Migrations (DM): Conceptualization VI (Data Migration Layer)

Data Migrations Series

Besides migrating the master and transactional data from the legacy systems there are usually three additional important business requirements for a Data Migration (DM) – migrate the data within expected timeline, with minimal disruption for the business, respectively within expected quality levels. Hence, DM’ timeline must match and synchronize with main project’s timeline in terms of main milestones, though the DM needs to be executed typically within a small timeframe of a few days during the Go-Live. In what concerns the third requirement, even if the data have high quality as available in the source systems or provided by the business, there are aspects like integration and consistency that rely primarily on the DM logic.

To address these requirements the DM logic must reach a certain level of performance and quality that allows importing the data as expected. From project’s beginning until UAT the DM team will integrate the various information iteratively, will need to test the changes several times, troubleshoot the deviations from expectations. The volume of effort required for these activities can be overwhelming. It’s not only important for the whole solution to be performant but each step must be designed so that besides fast execution, the changes and troubleshooting must involve a minimum of overhead.

For better understanding the importance, imagine a quest game in which the character has to go through a labyrinth with traps. If the player made a mistake he’ll need to restart from a certain distant point in time or even from the beginning. Now imagine that for each mistake he has the possibility of going one step back try a new option and move forward. For some it may look like cheating though in this way one can finish the game relatively quickly. It would be great if executing a DM could allow the same flexibility.

Unfortunately, unless the data are stored between steps or each step is a different package, an ETL solution doesn’t provide the flexibility of changing the code, moving one step behind, rerunning the step and performing troubleshooting, and this over and over again like in the quest game. To better illustrate the impact of such approach let’s consider that the DM has about 40 entities and one needs to perform on average 20 changes per entity. If one is able to move forwards and backwards probably each change will take about a few minutes to execute the code. Otherwise rerunning a whole package can take 5-10 times or even more as this can depend on packages’ size and data volume. For 800 changes only an additional minute per change equates with 800 minutes (about 13 hours).

In exchange, storing the data for an entity in a database for the important points of the processing and implementing the logic as a succession of SQL scripts allows this flexibility. The most important downside is that the steps need to be executed manually though this is a small price to pay for the flexibility and control gained. Moreover, with a few tricks one can load deltas as in the case of a phased DM.

To assure that the consistency of the data is kept one needs to build for each entity a set of validation queries that check for duplicates, for special cases, for data integrity, incorrect format, etc. The queries can be included in the sequence of logic used for the DM. Thus, one can react promptly to each unexpected value. When required, the validation rules can be built within reports and used in the data cleaning process by users, or even logged periodically per entity for tracking the progress.

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Data Migrations (DM): Conceptualization V (Data Extraction Layer)

ETL tools are ideal for extracting the needed data from the legacy system(s). They offer a considerable number of connectors to standard databases that leverage legacy systems’ data access layers or own frameworks, both categories providing acceptable performance for a wide range of solutions. Otherwise, third-party connectors can be considered as well, though their advantage might reside in the extra features they bring out-of-the-box in the detriment of performance loss, and thus should be used with caution.

Besides that, ETL tools provide also rich visual functionality that allow users building complex pipelines with transformations that process the data as data go through the pipeline. Further features like data profiling or cleansing bring additional benefits.

As usually only a subset of the legacy data is needed for the migration, an ETL solution allows extracting only the data in scope as filtering and other logic can be used in the extraction mechanism. Whether one loads the tables or entities 1:1 or aggregates the data from multiple tables is a matter of choice, even if the former two approaches are usually recommended.

As alternative to an ETL tool is building own extraction layer based for example on a powerful data access layer like ADO.Net. This might prove to be a cheaper alternative especially when ETL capabilities aren’t needed. This depends also on the overall architectural approach. Attempting to build a desktop-based application for a DM can prove to be a foolhardy approach especially when dealing with a considerable volume of data. Moreover, it would be needed to build features that are already available in ETL tools (transformations, workflows) or databases (indexes for performance optimization, join-based logic).

When the volume of data exceeds the capabilities of ETL tools one can consider ELT tools which load first the data before applying any transformations on them. Such tools are designed for the processing of what is known as big data (data having high volume, high velocity, high variety and different veracity).

When considering the best data extraction approach, it’s important to know where the data will be stored for processing. Given that DMs are data processing intensive the best data storage solution for processing would be a modern relational database. Besides performance, scalability, security, concurrency, failover mechanism some databases offer the possibility to connect directly to other servers via server links functionality. Despite this latter feature an ETL tool can still have considerable advantages for data extraction.

On the other side the DM logic can be in theory built entirely in the ETL tool without storing the data within a database, though this adds a high overhead on the server resources on which the solution runs as all the data needed for processing need to be loaded in memory. Even if the data are loaded in batches and processed as the batches go through the pipeline, the complexity of the processing can make challenging implementing any optimization techniques directly into the ETL tool. Moreover, fully ETL-based solutions are difficult to troubleshoot and change as the requirements change.

To address the high resources’ consumption of the ETL tools one can store the intermediary results into database tables on which indexes can be created for performance optimization. Moreover, the logic can be encapsulated in database objects and used in the processing. This approach enables troubleshooting, performing validations and restarting the processing from a given step in the detriment of splitting the logic between multiple ETL packages. This can be an acceptable price to pay for more flexibility. Given that most ETL transformations can be replaced with SQL-based logic the ETL tool can be used only for data extraction.

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Data Migrations (DM): Conceptualization IV (Data Access)

Data Migrations Series

Once the data sources for a Data Migration (DM) were identified the first question is how the data can be accessed. The legacy systems relying on ODBC-based databases are in theory relatively easy to access as long they allow the direct access to their data, which would enable thus a pull strategy. Despite this, there are organizations that don’t allow the direct access to the data even for read-only operations, being preferred to push the data directly to the consumers (aka push strategy) or push the data to a given location from where the consumer can use the data as needed (aka hybrid strategy). 

The direct access to the data allows in theory the best flexibility as the solution can extract the data when needed and this especially important during the initial phases of the project when the data need to be pulled more frequently until the requirements and logic is stabilized. A push strategy tends to add additional overhead as usually somebody else oversees the data exports, respectively the data need to be prepared in the expected format. On the other side, it would make sense to make an exception for a DM and allow the direct access to the data. 

 Hybrid strategies tend to be more complex and require additional resources or overhead as the data are stored temporarily at a separate location. Unfortunately, in certain scenarios this is the only approach can be used. Are preferred data files that allow keeping the integrity of the data and facilitate data consumption. Therefore, tabular text files or JSON files are preferred in the detriment of XML or Excel files. It’s preferable to export one data structure individually then storing parent-child solutions even if the latter can prove to be useful in certain scenarios. When there’s no other solution one can use also the standard reports available in the legacy systems.

When storing data outside the legacy systems for further processing it’s recommended to follow organization’s best practices, respectively to address the data security and privacy requirements. ETL tools allows accessing data from password protected areas like FTP, OneDrive or SharePoint. The fewer security layers in between the lower is in theory the overhead. Therefore, given its stability and simplicity FTP might prove to be a better storage solution than OneDrive, SharePoint or other similar technologies.

Ideally the extraction/export mechanisms should use the database objects that encapsulate already the logic in the legacy systems otherwise the team will need to reengineer the logic – for master data this can prove to be easy, though the logic of transactional data like on-hand or open invoices can be relatively complex to reengineer. Otherwise, the logic can be implemented directly in the extraction/export mechanisms or sometimes is more advisable to create database objects (usually on a different schema) on the legacy systems and just call the respective objects. 

When connecting directly to the data source it’s advisable using the data provider which allows the best performance and flexibility, however several tests might be needed to determine the best fit. It would be useful to check the limitations of each provider and find a stable driver version.  OLEDB and ADO.Net data providers provide in general a good performance, though native drivers of the legacy systems can be a better option upon case. 

Some legacy systems allow the access to their data only via service-based technologies like OData. OData tends to have poor performance for large data exports than standard access methods and therefore not indicated in such scenarios. In such cases might be a good idea to export the data directly from the legacy system. 

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Data Migrations (DM): Conceptualization III (Heuristics)

Probably one of the most difficult things to learn as a technical person is using the right technology for a given purpose, this mainly because one’s inclined using the tools one knows best. Moreover, technologies’ overlapping makes the task more and more challenging, the difference between competing technologies often residing in the details. Thus, identifying the gaps resumes in understanding the details of the problem(s) or need(s), respectively the advantages or disadvantages of a technology over the other. This is true especially about competing technologies, including the ones that replace other technologies.

There are simple heuristics, that can allow approaching such challenges. For example, heavy data processing belongs usually in databases, while import/export functionality belongs in an ETL tool.  Therefore, one can start looking at the problems from these two perspectives. Would the solution benefit from these two approaches or are there more appropriate technologies (e.g. data streaming, ELT, non-relational databases)? How much effort would involve building the solution? 

Commercial Off-The-Shelf (COTS) tools provided by third-party vendors usually offer specialized functionality in each area. Gartner and Forrester provide regular analyses of the main players in the important areas, analyses which can be used in theory as basis for further research. Even if COTS tend to be more expensive and can have some important functionality gaps, as long they are extensible, they can prove a good starting point for developing a solution. 

Sometimes it helps researching on the web what other people or organizations did, how they approached the same aspects, what technologies, techniques and best practices they used to overcome the challenges. One doesn’t need to reinvent the wheel even if it’s sometimes fun to do so. Moreover, a few hours of research can give one a basis of useful information and a better understanding over the work ahead.

On the other side sometimes it’s advisable to use the tools one knows best, however this can lead also to unusable and less performant solutions. For example, MS Excel and Access have been for years the tools of choice for building personal solutions that later grew into maintenance nightmares for the IT team. Ideally, they can still be used for data entry or data cleaning, though building solutions exclusively based on (one of) them can prove to be far than optimal. 

When one doesn’t know whether a technology or mix of technologies can be used to provide a solution, it’s recommended to start a proof-of-concept (PoC) that would allow addressing most important aspects of the needed solution. One can start small by focusing on the minimal functionality needed to check the main aspects and evolve the PoC during several iterations as needed.

For example, in the case of a Data Migration (DM) this would involve building the data extraction layer for an entity, implement several data transformations based on the defined mappings, consider building a few integrity rules for validation, respectively attempt importing the data into the target system. Once this accomplished, one can start increasing the volume of data to check how the solution behaves under stress. The volume of data can be increased incrementally or by considering all the data available. 

As soon the skeleton was built one can consider all the mappings, respectively add several entities to build the dependencies existing between them and other functionality. The prototype might not address all the requirements from the beginning, therefore consider the problems as they arise. For example, if the volume of data seems to cause problems then attempt splitting the data during processing in batches or considering specific optimization techniques like indexing or scaling techniques like increasing computing resources. 

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Data Migrations (DM): Conceptualization II (Plan vs. Concept vs. Strategy)

Data Migrations Series

A concept is a document that describes at high level the set of necessary steps and their implications to achieve a desired result, typically making the object of a project. A concept is usually needed to provide more technical and nontechnical information about the desired solution, the context in which a set of steps are conducted, respectively the changes considered, how the changes will be implemented and the further aspects that need to be considered. It can include a high-level plan and sometimes also information that typically belong in a Business Case – goals,objectives, required resources, estimated effort and costs, risks and opportunities.

A concept is used primarily as basis for sign-off as well for establishing common ground and understanding. When approved, it’s used for the actual implementation and solution’s validation. The concept should be updated as the project progresses, respectively as new information are discovered.

Creating a concept for a DM can be considered as best practice because it allows documenting the context, the technical and organizational requirements and dependencies existing between the DM and other projects, how they will be addressed. The concept can include also a high-level plan of the main activities (following to be detailed in a separate document).

Especially when the concept has an exploratory nature (due to incomplete knowledge or other considerations), it can be validated with the help of a proof-of-concept (PoC), the realization of a high-level-design prototype that focuses on the main characteristics of the solution and allows thus identifying the challenges. Once the PoC implemented, the feedback can be used to round out the concept.

Building a PoC for a DM should be considered as objective even when the project doesn’t seem to meet any major challenges. The PoC should resume in addressing the most important DM requirements, ideally by implementing the whole or most important aspects of functionality (e.g. data extraction, data transformations, integrity validation, respectively the import into the target system) for one or two data entities. Once the PoC built, the team can use it as basis for the evolutive development of the solution during the iterations considered.

A strategy is a set of coordinated and sustainable actions following a set of well-defined goals, actions devised into a plan and designed to create value and overcome further challenges. A strategy has the character of a concept though it has a broader scope being usually considered when multiple projects or initiatives compete for the same resources to provide a broader context and handle the challenges, risks and opportunities. Moreover, the strategy takes an inventory of the current issues and architecture – the 'AS-IS' perspective and sketches the to 'TO-BE' perspective by devising a roadmap that bridges the gap between the two.

In the case of a DM a strategy might be required when multiple DM projects need to be performed in parallel or sequentially, as it can help the organization to better manage the migrations.

A plan is a high-level document that describes the tasks, schedule and resources required to carry on an activity. Even if it typically refers to the work or product breakdown structure, it can cover other information usually available in a Business Case. A project plan is used to guide both project execution and project control, while in the context of Strategic Management the (strategic) plan provides a high-level roadmap on how the defined goals and objectives will be achieved during the period covered by the strategy.

For small DM projects a plan can be in theory enough. As both a strategy and a concept can include a high-level plan, the names are in praxis interchangeable.

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Data Migrations (DM): Conceptualization I (Goals, Objectives & Requirements)

Data Migrations Series

One of the nowadays’ challenges is finding the right mix of technologies that allows building a solution for a business need. There are so many choices and the responsible person is easily tempted to use one of the trending technologies just because he wants to learn something new or the technologies seem to fit into the bigger picture, which probably in many cases it would be acceptable. Unfortunately, there’s also the tendency of picking a technology without looking at what functionality it provides, respectively whether the functionality meets intended solutions’ requirements. Moreover, the requirements are sometimes barely defined at the appropriate level of detail, fact that makes from the implementation project a candidate for failure. Sometimes even the goals and objectives aren’t clearly stated, fact that can make a project’s success easily questionable from the beginning. 

A goal is a general statement that reflects the desired result toward which an organization’s effort needs to be directed. For example, a Data Migration (DM)’s primary goal can be formulated as 'to make available all the master and transactional data needed by the business from the legacy systems to the target system(s) within expected timeline and quality with a minimal disruption for the business'. 

An objective is a break down of the goal into several components that should foster a clear understanding on how the goal will be achieved. Ideally the objectives should be SMART (specific, measurable, attainable, relevant, time-bound), even if measurable objectives are sometimes hard to define properly. One can consider them as the tactics used in achieving the goal. For example, the above formulated goal can be broken down into the following objectives:

• Build a DM concept/strategy
• Build a flexible and performant infrastructure for DM that can be adapted to further requirements
• Provide a basis for further DMs
• Align DM and main project’s requirements and activities
• Provide an interface and support for the Data Management areas
• Foster trust, transparency and awareness 
• Address internal/external compliance requirements
• Document and communicate accountability for the various activities
• Cleanse and enrich the data needed by the target system 
• Archive the DM and project data 

One can attempt defining the objectives directly from the goal(s), though unless one is aware of all the implication a DM has, more likely one will be forced to define and evaluate the individual functional and nonfunctional requirements for the DM first, and attempt consolidating the requirements into a set of objectives. In the end it can be a combination of both, in which some objectives are first formulated, the requirements are defined and evaluated, respectively the objectives are refined to accommodate the requirements. 

ISO 9126, an international standard for the evaluation of software quality, defines about 45-50 attributes that can be used for addressing the requirements of software solutions, attributes that reflect functionality, reliability, usability, efficiency, and maintainability characteristics. One can start with such a list and identify how important are the respective attributes for the solution.  The next step would be to document the requirements into a consolidated list by providing a short argumentation for their use, respectively how they will be addressed as part of the solution. The process can prove to be time-consuming, however it is a useful exercise that usually needs to be done only once and be reviewed occasionally.

The list can be created independently of any other documentation or be included directly into a concept or strategy. The latter will assure in theory that the document provides a unitary view of the migration, considering that each new or obsolete requirement can impact the concept. 

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Data Migrations (DM): Quality Acceptance Criteria V

Efficiency 

Efficiency is the degree to which a solution uses the hardware (storage, network) and other organizational resources to fulfill a given task. Data characterized by high volume, velocity, variety and veracity can be challenging to process, requiring upon case more processing power. Therefore, the DM solutions need to consider these aspects as well. However, efficiency refers on whether the available resources are used efficiently – the waste in terms of resource utilization is minimal. 

On the other side the waste of resources can be acceptable when there are other benefits or requirements that need to be considered, respectively when the ratio between resources utilization and effort to built more efficient processes is acceptable.

A DM solution involves iterative and exploratory processes in which knowledge and feedback is integrated in each iteration, therefore it might look like resources are not used efficiently. However, this is a way to handle complexity and uncertainty by breaking the effort in manageable chunks.

Learnability

Learnability is the degree to which a person can become familiar with a solution’s use, the data and the processes associated with it. A DM can be challenging for many technical and non-technical resources as it requires a certain level of skillset and understanding of the requirements, needs and deliverables. The complexity of the data and requirements can be overwhelming, however with appropriate communication and awareness established, the challenges can be overcome. 

Stability

Stability is the degree to which a solution is sensitive to environment changes (e.g. overuse of resource, hardware or software failures, updates), respectively on whether it performs with no performance defects or it does not crash under defined levels of stress. Stability can be monitored during the various phases and countermeasures need to be considered in case the solution is not stable enough (e.g. redesigning the solution, breaking the data in smaller chunks)

Suitability 

Suitability is the degree to which a solutions provides functions that meet the stated and implied needs. No matter how performant and technologically advanced a solution is, it brings less value as long it doesn’t perform what it was intended to do.

Transparency 

Transparency is the degree to which a solution’s stakeholders have access to the requirements, processes, data, documentation, or other information required by them. In a DM transparency is important especially important in respect to the data, logic and rules used in data processing, respectively the number of records processed. 

Trustability

Trustability is the degree to which a solution can be trusted to provide the expected results. Even if the technical team assures that the solution can deliver what was indented, the success of a DM is a matter of perception from stakeholders’ perspective. Providing transparency into the data, rules and processes can improve the level of trust however, special attention need to be given to the issues raised by stakeholders during and after Go-Live, as differences need to be mitigated. 

Understandability 

Understandability is the degree to which the requirements of a solution were understood by the resources involved in terms of what needs to be performed. For the average project resource it might be challenging to understand the implications of a DM, and this can apply to technical as well non-technical resources. Making people aware of the implications is probably one of the most important criteria for success, as the success of a migration is often a matter of perception. 

Usability 

Usability is the degree to which a solution can be used by the targeted users within the agreed context of usage. Ideally DM solutions need to be easy to use, though there are always trade-offs. In the end, a DM must fit the purpose it was built for. 

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Data Migrations (DM): Quality Acceptance Criteria IV

Data Migrations Series

Reliability

Reliability is the degree to which a solution performs its intended functions under stated conditions without failure. In other words, a DM is reliable if it performs what was intended by design. The data should be migrated only when migration’s reliability was confirmed by the users as part of the sign-off process. The dry-runs as well the final iteration for the UAT have the objective of confirming solution’s reliability.

Reversibility

Reversibility is the degree to which a solution can return to a previous state without starting the process from the beginning. For example, it should be possible to reverse the changes made to a table by returning to the previous state. This can involve having a copy of the data stored respectively deleting and reloading the data when necessary. 

Considering that the sequence in which the various activities is fix, in theory it’s possible to address reversibility by design, e.g. by allowing to repeat individual steps or by creating rollback points. Rollback points are especially important when loading the data into the target system. 

Robustness

Robustness is the degree to which the solution can accommodate invalid input or environmental conditions that might affect data’s processing or other requirements (e,g. performance). If the logic can be stabilized over the various iterations, the variance in data quality can have an important impact on a solutions robustness. One can accommodate erroneous input by relaxing schema’s rules and adding further quality checks.

Security 

Security is the degree to which the DM solution protects the data so that only authorized people have access to the respective data to the defined level of authorization as data are moved through the solution. The security provided by a solution needs to be considered against the standards and further requirements defined within the organization. In case no such standards are available, one can in theory consider the industry best practices.

Scalability

Scalability is the degree to which the solution is able to respond to an increased workload.  Given that the number of data considered during the various iterations vary in volume, a solution’s scalability needs to be considered in respect to the volume of data to be migrated.  

Standardization

Standardization is the degree to which technical standards were implemented for a solution to guarantee certain level of performance or other aspects considered as import. There can be standards for data storage, processing, access, transportation, or other aspects associated with the migration processes. Moreover, especially when multiple DMs are in scope, organizations can define a set of standards and guidelines that should be further considered.  

Testability

Testability is the degree to which a solution can be tested in the respect to the set of functional and data-related requirements. Even if for the success of a migration are important the data in their final form, to achieve that is needed to validate the logic and test thoroughly the transformations performed on the data. As the data go trough the data pipelines, they need to be tested in the critical points – points where the data suffer important transformations. Moreover, one can consider record counters for the records processed in each such critical point, to assure that no record was lost in the process.  

Traceability

Traceability is the degree to which the changes performed on the data can be traced from the target to the source systems as record, respectively at entity level. In theory, it’s enough to document the changes at attribute level, though upon case it might needed to document also the changes performed on individual values. 

Mappings at attribute level allow tracing the data flow, while mappings at value level allow tracing the changes occurrent within values. 

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Data Migrations (DM): Quality Acceptance Criteria III

Data Migrations Series

Repeatability

Repeatability is the degree with which a DM can be repeated and obtain consistent results between repetitions. Even if a DM is supposed to be a one-time activity for a project, to guarantee a certain level of quality it’s important to consider several iterations in which the data requirements are refined and made sure that the data can be imported as needed into the target system(s). Considered as a process, as long the data and the rules haven’t changed, the results should be the same or have the expected level of deviation from expectations. 

This requirement is important especially for the data migrated during UAT and Go-Live, time during which the input data and rules need to remain frozen (even if small changes in the data can still occur). In fact, that’s the role of UAT – to assure that the data have the expected quality and when compared to the previous dry-run, that it attains the expected level of consistency. 

Reusability

Reusability is the degree to which the whole solution, parts of the logic or data can be reused for multiple purposes. Master data and the logic associated with them have high reusability potential as they tend to be referenced by multiple entities. 

Modularity

Modularity is the degree to which a solution is composed of discrete components such that a change to one component has minimal impact on other components. It applies to the solution itself but also to the degree to which the logic for the various entities is partitioned so to assure a minimal impact. 

Partitionability

Partitionability is the degree to which data or logic can be partitioned to address the various requirements. Despite the assurance that the data will be migrated only once, in practice this assumption can be easily invalidated. It’s enough to increase the system freeze by a few days and/or to have transaction data that suddenly requires master data not considered. Even if the deltas can be migrated in system manually, it’s probably recommended to migrate them using the same logic. Moreover, the performing of incremental loads can be a project requirement. 

Data might need to be partitioned into batches to improve processing’s performance. Partitioning the logic based on certain parameters (e.g. business unit, categorical values) allows more flexibility in handling other requirements (e.g. reversibility, performance, testability, reusability). 

Performance

Performance refers to the degree a piece of software can process data into an amount of time considered as acceptable for the business. It can vary with the architecture and methods used, respectively data volume, veracity, variance, variability, or quality.

Performance is a critical requirement for a DM, especially when considering the amount of time spent on executing the logic during development, tests and troubleshooting, as well for other activities. Performance is important during dry-runs but more important during Go-Live, as it equates with a period during which the system(s) are not available for the users. Upon case, a few hours of delays can have an important impact on the business. In extremis, the delays can sum up to days. 

Predictability

Predictability is the degree to which the results and behavior of a solution, respectively the processes involve are predictable based on the design, implementation or other factors considered (e.g. best practices, methodology used, experience, procedures and processes). Highly predictable solutions are desirable, though reaching the required level of performance and quality can be challenging. 

The results from the dry-runs can offer an indication on whether the data migrated during UAT and Go-Live provide a certain level of assurance that the DM will be a success. Otherwise, an additional dry-run should be planned during UAT, if the schedule allows it.

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Data Migrations (DM): Quality Acceptance Criteria II

Data Migrations Series

Auditability

Auditability is the degree to which the solution allows checking the data for their accuracy, or for their quality in general, respectively the degree to which the DM solution and processes allow to be audited regarding compliance, security and other types of requirements. All these aspects are important in case an external sign-off from an auditor is mandatory. 

Automation

Automation is the degree to which the activities within a DM can be automated. Ideally all the processes or activities should be automated, though other requirements might be impacted negatively. Ideally, one needs to find the right balance between the various requirements. 

Cohesion

Cohesion is the degree to which the tasks performed by the solution, respectively during the migration, are related to each other. Given the dependencies existing between data, their processing and further project-related activities, DM imply a high degree of cohesion that need to be addressed by design. 

Complexity 

Complexity is the degree to which a solution is difficult to understand given the various processing layers and dependencies existing within the data. The complexity of DM revolve mainly around the data structures and the transformations needed to translate the data between the various data models. 

Compliance 

Compliance is the degree to which a solution is compliant with internal or external regulations that apply. There should be differentiated between mandatory requirements, respectively recommendations and other requirements.

Consistency 

Consistency is the degree to which data conform to an equivalent set of data, in this case the entities considered for the DM need to be consistent to each other. A record referenced in any entity of the migration need to be considered, respectively made available in the target system(s) either by parametrization or migration. 

During each iteration, the data need to remain consistent, so it can facilitate the troubleshooting. The data are usually reimported between iterations or during same iteration, typically to reflect the changes occurred in the source systems or other purposes. 

Coupling 

Data coupling is the degree to which different processing areas within a DM share the same data, typically a reflection of the dependencies existing between the data. Ideally, the areas should be decoupled as much as possible. 

Extensibility

Extensibility is the degree to which the solution or parts of the logic can be extended to accommodate further requirements. Typically, this involves changes that deviate from the standard functionality. Extensibility impacts positively the flexibility.

Flexibility 

Flexibility is the degree to which a solution can handle new requirements or ad-hoc changes to the logic. No matter how good everything was planned there’s always something forgotten or new information is identified. Having the flexibility to change code or data on the fly can make an important difference. 

Integrity 

Integrity is the degree to which a solution prevents the changes to data besides the ones considered by design. Users and processes should not be able modifying the data besides the agreed procedures. This means that the data need to be processed in the sequence agreed. All aspects related to data integrity need to be documented accordingly. 

Interoperability 

Interoperability is the degree to which a solution’s components can exchange data and use the respective data. The various layers of a DM’s solutions must be able to process the data and this should be possible by design. 

Maintainability

Maintainability is the degree to which a solution can be modified to or add minor features, change existing code, corrects issues, refactor code, improve performance or address changes in environment. The data required and the transformation rules are seldom known in advance. The data requirements are definitized during the various iterations, the changes needing to be implemented as the iterations progress. Thus, maintainability is a critical requirement.

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