MSSQL-REC-WORKERS-001 · Worker threads near the limit

Severity	Confidence	Permission	Applies to
High	Confirmed	VIEW SERVER STATE	Recordings (codedb-lens record): SQL Server 2017+, Azure SQL MI, RDS

What it checks

The workers collector: worker threads in sys.dm_os_schedulers as a percentage of max_workers_count. An episode is two or more samples in a row at 90% or more (max_pct).

Why it matters

SQL Server used 90% or more of its worker threads for at least 30 seconds. When they run out, new requests wait (THREADPOOL) and even new connections can fail, while the CPU may look idle.

Next action

The usual cause is blocking (many sessions stuck behind one) or heavy parallelism. Check the blocking and wait findings of the same period first; do not raise max worker threads before finding the cause.

How to verify

Record again during the same hours after the fix. Workers must stay well below max_workers.

Limitations

Counts threads created by SQL Server, which stay around for a while after a peak.