SQL Server must limit the use of resources by priority and not impede the host from servicing processes designated as a higher priority.

Priority protection helps prevent a lower-priority process from delaying or interfering with the information system servicing any higher-priority process. This control does not apply to components in the information system for which there is only a single user/role. The application must limit the use of resources by priority.

SQL Server often runs queries for multiple users at the same time. If lower priority processes are utilizing a disproportionately high amount of database resources, this can severely impact higher priority processes.

Even if SQL Server's utilization is very small and there may seem to be no need to priority protection, often resources grow exponentially and must be implemented as part of an initial deployment.