SLA Full Form is Service Legal Agreement. SLA is a legal contract between a customer and a service provider. This creates a commitment for a service provider to maintain a certain level of service. The agreement must contain a certain level of support and service options, penalty or enforcement for the services not provided. It also has to have a warranted system performance related to up time or downtime; a certain standard of customer support, etc.
SLA also has to specify the details of hardware or software or other services provided and the fee for the same. In addition to all these performance metrics, the SLA might include a clear plan with documentation of how a service provider would compensate during events of breaching of a contract. Once a SLA is established, it has to be reviewed periodically to reflect the changes in any new regulations or changes in technology.