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HADR_TRANSPORT_FLOW_CONTROL is an Availability Group primary pausing sends to one replica because too many messages to it are unacknowledged, and this page shows how to tell it from database flow control and find the replica.

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⏳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 primary pausing sends for a database because too many messages to a secondary are still unacknowledged. It is only an issue if network sends are slower than expected. Run the…

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⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: HADR_SYNC_COMMIT Wait TypeRelated pillar: High Availability Is It a Problem? Normally no. It is commonly filtered as benign, and Get Wait Statistics filters it out by default. Our SQL Server 2025 lab, with no Availability Group, still recorded 22 waits totalling…

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⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: HADR_SYNC_COMMIT Wait TypeRelated pillar: High Availability Is It a Problem? Rarely. It is not a known contention point, because Availability Group configuration changes are infrequent. Get Wait Statistics does not filter it out, so if it ranks, you will see it.…

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⏳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 waits share this page: FT_IFTSHC_MUTEX: Microsoft describes it as full-text waiting on an FDHost control operation, documented for information only. It is full-text worker threads synchronising with each other, for example…

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⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: SOS_SCHEDULER_YIELD Wait TypeRelated pillar: Performance & Troubleshooting Is It a Problem? No. It can be safely ignored, and Get Wait Statistics filters it out by default. It says nothing about full-text performance, even on servers that use the feature heavily. What…

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⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: IO_COMPLETION Wait TypeRelated pillar: Performance & Troubleshooting Two FileTable waits share this page. Both are documented as internal use only, from SQL Server 2012: FFT_NSO_DB_LIST: waiting for access to the list of databases the FileTable subsystem maintains; examples include shutting down…

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⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: IO_COMPLETION Wait TypeRelated pillar: High Availability Two waits synchronise I/O against database snapshot sparse files, and this page covers both. The definitions are Microsoft’s: FCB_REPLICA_READ: the reads of a snapshot (or a temporary snapshot created by DBCC) sparse file are synchronized.…

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⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: CXPACKET and CXCONSUMER Wait TypesRelated pillar: Performance & Troubleshooting Is It a Problem? Rarely. It is not a known contention point and filters it as benign; our SQL Server 2025 lab had about 3,250 waits totalling 15 seconds in a day.…

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⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: CXPACKET and CXCONSUMER Wait TypesRelated pillar: Performance & Troubleshooting Is It a Problem? Treat it like CXPACKET: evidence of parallel queries, not proof of a problem. It was zero on our SQL Server 2025 lab, where the CX waits carry the…

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