"A signed agreement of system service requirements between two parties (such as your company and an ASP or between your department and end users) that defines the guidelines, response times, actions, and so on, that will be adhered to for the life of the agreement." (Allan Hirt et al, "Microsoft SQL Server 2000 High Availability", 2004)
"A contract with a service provider, be it an internal IT organization, application service provider, or outsourcer, that specifies discrete reliability and availability requirements for an outsourced system. An SLA might also include other requirements such as support of certain technology standards or data volumes. An outsourcer’s failure to adhere to the terms laid out in an SLA could result in financial penalties." (Evan Levy & Jill Dyché, "Customer Data Integration", 2006)
"A formal negotiated agreement between two parties. It is a contract that exists between customers and their service provider, or between service providers. It records the common understanding about services, priorities, responsibilities, guarantees, and so on, with the main purpose to agree on the level of service." (Tilak Mitra et al, "SOA Governance", 2008)
"An agreement between a customer and a product or service provider that defines conditions under which the provider will offer support or additional services to the customer, and what level of services will be offered under each of those conditions." (Steven Haines, "The Product Manager's Desk Reference", 2008)
"An agreement between a service provider and a service recipient that formally defines the levels of service that are to be provided." (David G Hill, "Data Protection: Governance, Risk Management, and Compliance", 2009)
"A formal negotiated agreement between two parties that usually records the common understanding about priorities, responsibilities, and warranties, with the main purpose of agreeing on the quality of the service. For example, an SLA may specify the levels of availability, serviceability, performance, operation, or other attributes of the service (such as billing and even penalties in the case of violations of the SLA)." (David Lyle & John G Schmidt, "Lean Integration", 2010)
"A written legal contract between a service provider and client wherein the service provider guarantees a minimum level of service." (Linda Volonino & Efraim Turban, "Information Technology for Management" 8th Ed., 2011)
"A contracted guarantee of service delivery for a program, transaction, service, or workload." (Craig S Mullins, "Database Administration", 2012)
"The part of a contract between two parties that outlines the delivery of services within defined timeframes." (DAMA International, "The DAMA Dictionary of Data Management", 2011)
"A statement to customers or the user community about the service the IT department will provide. It can refer to a variety of metrics, such as performance, up-time, resolution time, and so on." (Bill Holtsnider & Brian D Jaffe, "IT Manager's Handbook" 3rd Ed., 2012)
"An agreement between an IT service provider and a customer to provide a specific level of reliability for a service. It stipulates performance expectations such as minimum uptime and maximum downtime levels. Many SLAs include monetary penalties if the IT service provider does not provide the service as promised." (Darril Gibson, "Effective Help Desk Specialist Skills", 2014)
"The service or maintenance contract that states the explicit levels of support, response time windows or ranges, escalation procedures in the event of a persistent problem, and possible penalties for nonconformance in the event the vendor does not meet its contractual obligations." (Robert F Smallwood, "Information Governance: Concepts, Strategies, and Best Practices", 2014)
"A contract for formally defined services. Particular aspects of the service (scope, quality, responsibilities) are agreed between the service provider and the service user. A common feature of an SLA is a contracted delivery time of the service or performance." (Thomas C Wilson, "Value and Capital Management", 2015)
"A portion of a service contract that promises specific levels of service." (Weiss, "Auditing IT Infrastructures for Compliance" 2nd Ed, 2015)
"A contract between a service provider (either internal or external) and the end user that defines the level of service expected from the service provider." (Project Management Institute, "A Guide to the Project Management Body of Knowledge (PMBOK® Guide)", 2017)
