🛢DBMS: Concurrency Control (Definitions)

"The control of concurrent access. SQL Server uses locking to allow multiple users to access and change shared data at the same time without conflicting with one another." (Microsoft Corporation, "SQL Server 7.0 System Administration Training Kit", 1999)

"Concurrency control is the control on the database and transactions which are executed concurrently to ensure that each transaction completed healthy." (S. Sumathi & S. Esakkirajan, "Fundamentals of Relational Database Management Systems", 2007)

"Concurrency control ensures that database operations can be executed concurrently without compromising correctness. Pessimistic concurrency control, such as used in systems with locks, will block any potentially conflicting operations even if they may not turn out to actually conflict. Optimistic concurrency control, the approach used by WiredTiger, will delay checking until after a conflict may have occurred, aborting and retrying one of the operations involved in any write conflict that arises." (MongoDb, "Glossary", 2008)

"Mechanisms to ensure that a database remains consistent and accurate during concurrent use." (Jan L Harrington, "Relational Database Design and Implementation" 3rd Ed., 2009)

"A DBMS feature that is used to coordinate the simultaneous execution of transactions in a multiprocessing database system while preserving data integrity." (Carlos Coronel et al, "Database Systems: Design, Implementation, and Management" 9th Ed., 2011)

"The control of process contention for resources within multi-process systems." (DAMA International, "The DAMA Dictionary of Data Management", 2011)

🛢DBMS: Lock/Locking (Definitions)

"The process of restricting access to resources in a multi-user environment to maintain security and prevent concurrent access problems. SQL Server automatically applies locks to tables or pages." (Karen Paulsell et al, "Sybase SQL Server: Performance and Tuning Guide", 1996)

"SQL Server issues locks to prevent users from interfering with each other's work." (Owen Williams, "MCSE TestPrep: SQL Server 6.5 Design and Implementation", 1998)

"A restriction on access to a resource in a multiuser environment. SQL Server locks users out of a specific record, field, or file automatically to maintain security or prevent concurrent data manipulation problems." (Microsoft Corporation, "SQL Server 7.0 System Administration Training Kit", 1999)

"A method the DBMS uses to prevent concurrent transactions from interfering with one another. Physically, a lock is one of three things: a latch, a mark on the wall, or a RAM record." (Peter Gulutzan & Trudy Pelzer, "SQL Performance Tuning", 2002)

"A method of ensuring concurrency. Locking enables users to temporarily "check out" an object, preventing other users from changing the object, for the purpose of ensuring consistency." (Thomas Moore, "EXAM CRAM™ 2: Designing and Implementing Databases with SQL Server 2000 Enterprise Edition", 2005)

"SQL Server uses locks to prevent multiple users from modifying the same data at the same time." (Joseph L Jorden & Dandy Weyn, "MCTS Microsoft SQL Server 2005: Implementation and Maintenance Study Guide - Exam 70-431", 2006)

"A mechanism used by a concurrent system to prevent data anomalies by isolating transactions from each other." (Marilyn Miller-White et al, "MCITP Administrator: Microsoft® SQL Server™ 2005 Optimization and Maintenance 70-444", 2007)

"A lock is an access restriction placed on part of a database to prevent other users or processes from viewing or modifying data as it is being viewed or modified by one process. Locks can be placed on rows, pages, extents, tables, or databases." (Darril Gibson, "MCITP SQL Server 2005 Database Developer All-in-One Exam Guide", 2008)

"MongoDB uses locks to ensure that concurrency does not affect correctness. MongoDB uses read locks, write locks and intent locks. For more information, see What type of locking does MongoDB use?." (MongoDb, "Glossary", 2008)

"Used to control access to part of the database. For example, while one user updates a row, the database places a lock on the row so other users cannot interfere with the update. Different databases may lock data by rows, table, or disk page." (Rod Stephens, "Beginning Database Design Solutions", 2008)

"The processing of giving a transaction exclusive rights to view and/or update a database element to prevent problems that arise with interleaved transaction execution." (Jan L Harrington, "SQL Clearly Explained 3rd Ed. ", 2010)

"A DBMS function used to ensure the integrity of data. When a database resource is locked by one process, another process is not permitted to change the locked data. Locking is necessary to enable the DBMS to facilitate the ACID properties of transaction processing." (Craig S Mullins, "Database Administration: The Complete Guide to DBA Practices and Procedures" 2nd Ed, 2012)

"A restriction on access to a resource in a multiuser environment." (Microsoft, "SQL Server 2012 Glossary", 2012)

"A means of preventing uncommitted changes made by one application process from being perceived by another application process and for preventing one application process from updating data that is being accessed by another process. A lock ensures the integrity of data by preventing concurrent users from accessing inconsistent data. A means of serializing a sequence of events or serializing access to data." (Sybase, "Open Server Server-Library/C Reference Manual", 2019)

"The process by which a DBMS restricts access to a row in a multiuser environment. The DBMS usually sets a bit on a row or the physical page containing a row that indicates the row or page is locked." (Microsoft) 

🌁Software Engineering: Concurrency (Definitions)

"The capability of having more than one computation in progress at the same time. These computations may be on separate cores or they may be sharing a single core by being swapped in and out by the operating system at intervals." (Clay Breshears, "The Art of Concurrency", 2009)

"the simultaneous or pseudo-simultaneous execution of multiple action sequences." (Bruce P Douglass, "Real-Time Agility: The Harmony/ESW Method for Real-Time and Embedded Systems Development", 2009)

"A model of computation with simultaneous sequences of computation and unpredictable interaction between the sequences. For example, two threads in an application that occasionally communicate. In contrast to parallelism, the apparent simultaneity might be an illusion, for example when the program executes on a single CPU with a single core. An example of the unpredictability of concurrency is the handling of asynchronous events, such as user input or network traffic. The precise sequence of execution steps that will occur in the entire program can’t be predicted in advance. Contrast with parallelism." (Dean Wampler, "Functional Programming for Java Developers", 2011)

"The shared use of resources by multiple interactive users or application processes at the same time." (IBM, "Informix Servers 12.1", 2014)

"measure of the number of users engaged in the same operation at the same time" (ITIL)

"performing and executing multiple tasks and processes at the same time." (Analytics Insight)

IT: Asynchronous (Definitions)

"Lack of temporal concurrence; not occurring at the same time." (Ruth C Clark & Chopeta Lyons, "Graphics for Learning", 2004)

"A process that is not coordinated in time. In data storage processes, asynchronous means that the device or software does not wait for acknowledgement before performing the next I/O." (Tom Petrocelli, "Data Protection and Information Lifecycle Management", 2005)

"Data that are transmitted without an associated clock signal. The time spacing between data characters or blocks may be of arbitrary duration (opposite of synchronous)." (John R Vacca, "Optical Networking Best Practices Handbook", 2006)

"The ability to send or receive calls independently and in any order." (Craig F Smith & H Peter Alesso, "Thinking on the Web: Berners-Lee, Gödel and Turing", 2008)

"Separate execution streams that can run concurrently in any order relative to each other are asynchronous." (Clay Breshears, "The Art of Concurrency", 2009)

"A system in which events can occur in any order, such as a game where different players can place their moves without being concerned about the order that other players are moving. Contrast with synchronous." (Jon Radoff, "Game On: Energize Your Business with Social Media Games", 2011)

"Describes a style of communication in which the initiator does not wait for a reply. Opposite of synchronous." (DAMA International, "The DAMA Dictionary of Data Management", 2011)

"A style of communication in which the initiator does not wait for a reply." (Craig S Mullins, "Database Administration", 2012)

"Not occurring at the same moment in time as some specific operation of the computer; in other words, not synchronized with the program’s actions" (Nell Dale & John Lewis, "Computer Science Illuminated" 6th Ed., 2015)

"Pertaining to events that are not synchronized in time or do not occur in regular or predictable time intervals." (Sybase, "Open Server Server-Library/C Reference Manual", 2019)