SQL Server error 8645, with a severity level of 17, typically indicates that the query execution was affected by a resource governor. It suggests that SQL Server did not have enough resources (e.g., CPU or memory) to execute the query due to server overload or intentionally imposed limits by Resource Governor.
The common accompanying message for this error is: 'A timeout occurred while waiting for memory resources to execute the query. Rerun the query.' This issue can be caused by heavy workloads, queries requiring an excessive amount of memory, inadequate server capacity configuration, contention between multiple concurrent queries competing for limited system resources, or a Resource Governor classifier configuration restricting certain queries from consuming large amounts of memory.
Common causes:
- Query Memory Allocation Failure, when executing complex or resource-intensive queries (such as sorts, joins on large datasets), additional workspace memory is required. If SQL Server cannot allocate sufficient memory in time because other processes are overburdening it—or due to configured thresholds—this timeout occurs.
- Resource Governor Settings, If you're using SQL Server's *Resource Governor*, specific workload groups may have restrictions placed on their maximum allowable resource usage levels (like `MAX_MEMORY_PERCENT`).
- Severity Level 17 Indicates it's likely an "environmental" issue rather than a problem with T-SQL syntax itself—a lack of available physical resources like CPU/memory/storage at runtime.
Check Query Performance and Execution Plan - Analyze specific problematic queries causing error #8645. - Use tools such as AI-DBA for SQL Server