Category: Wait Types

⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: HADR_SYNC_COMMIT Wait TypeRelated pillar: High Availability HADR_LOGCAPTURE_WAIT is recorded by the Availability Group log capture thread on the primary while it waits for log records to become available to ship to secondaries. If the capture thread has already sent everything up…

⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: HADR_SYNC_COMMIT Wait TypeRelated pillar: High Availability Two small Availability Group internals share this page: Both are single-purpose locks around infrequent events. Are They a Problem? No; neither has been a contention point. The subscriber-list lock is touched when replica events fire,…

⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: HADR_SYNC_COMMIT Wait TypeRelated pillar: High Availability HADR_GROUP_COMMIT is recorded when transaction commit processing on an Availability Group primary waits briefly so that multiple commit records can be packed into a single log block. Group commit is an optimisation: fewer, fuller log…

⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: HADR_SYNC_COMMIT Wait TypeRelated pillar: High Availability HADR_FILESTREAM_IOMGR_IOCOMPLETION is recorded by the FILESTREAM I/O manager for Availability Groups while it sleeps between checks for completed FILESTREAM sends to replicas. The detail that surprises people: it ticks every half second for half a…

⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: HADR_SYNC_COMMIT Wait TypeRelated pillar: High Availability HADR_DATABASE_FLOW_CONTROL is an Availability Group wait recorded on the primary when log capture has outrun the network send. Each database in an AG has a quota of unacknowledged messages allowed in flight to a secondary;…

⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: HADR_SYNC_COMMIT Wait TypeRelated pillar: High Availability HADR_CLUSAPI_CALL is recorded when a SQL Server thread switches to preemptive mode to invoke Windows Server Failover Clustering (WSFC) APIs. Availability Groups lean on the cluster constantly, health reporting, lease maintenance, metadata reads, failover coordination,…

⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: HADR_SYNC_COMMIT Wait TypeRelated pillar: High Availability HADR_AG_MUTEX is recorded when a thread waits for the critical section guarding an Availability Group’s configuration. AG DDL statements (ALTER AVAILABILITY GROUP, adding or removing databases and replicas) and Windows Server Failover Clustering commands need…

⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: SOS_SCHEDULER_YIELD Wait TypeRelated pillar: Performance & Troubleshooting Two internal full-text search waits share this page: FT_IFTSHC_MUTEX, a thread in a full-text operation synchronising with other full-text workers around fdhost control operations (fdhost.exe is the filter daemon host process that does the…

⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: SOS_SCHEDULER_YIELD Wait TypeRelated pillar: Performance & Troubleshooting FT_IFTS_SCHEDULER_IDLE_WAIT is recorded by the full-text search scheduler while it waits for work to appear on the full-text background task queue. If the Full-Text Engine is installed, this scheduler exists and mostly idles, whether…

⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: IO_COMPLETION Wait TypeRelated pillar: Performance & Troubleshooting Two waits belong to the FileTable subsystem (the FFT prefix), and this page covers both: FFT_NSO_DB_LIST, a thread waiting for access to the list of databases the FileTable subsystem maintains, and FFT_RECOVERY, a thread…