Author: Peter Whyte

  • HADR_WORK_POOL Wait Type in SQL Server

    ⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: HADR_SYNC_COMMIT Wait TypeRelated pillar: High Availability HADR_WORK_POOL is recorded when a thread waits for access to the Availability Group work queue object, the concurrency control around AG background workers getting into position to wait for work. It sits one step before…

    Written by

    Peter Whyte

  • HADR_TIMER_TASK Wait Type in SQL Server

    ⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: HADR_SYNC_COMMIT Wait TypeRelated pillar: High Availability HADR_TIMER_TASK is recorded around the Availability Group timer machinery: threads waiting for access to the list of AG timers, plus the deliberate waits between runs of periodic AG tasks. A task that runs every ten…

    Written by

    Peter Whyte

  • HADR_SEEDING_LIMIT_BACKUPS Wait Type in SQL Server

    ⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: HADR_SYNC_COMMIT Wait TypeRelated pillar: High Availability HADR_SEEDING_LIMIT_BACKUPS is recorded during Availability Group automatic seeding operations, and its observed behaviour is long waits, thousands of seconds in reported cases, lasting for the duration of some seeding runs. The name suggests throttling around…

    Written by

    Peter Whyte

  • HADR_NOTIFICATION_DEQUEUE Wait Type in SQL Server

    ⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: HADR_SYNC_COMMIT Wait TypeRelated pillar: High Availability HADR_NOTIFICATION_DEQUEUE is recorded by the background task that processes Windows Server Failover Clustering notifications while it waits for the next notification to arrive. Availability Groups need to hear about cluster events (node changes, resource moves,…

    Written by

    Peter Whyte

  • HADR_LOGPROGRESS_SYNC Wait Type in SQL Server

    ⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: HADR_SYNC_COMMIT Wait TypeRelated pillar: High Availability HADR_LOGPROGRESS_SYNC is recorded when a thread waits for exclusive access to the structure holding the latest log-harden LSN on an Availability Group primary with a synchronous replica. That structure is the release gate for synchronous…

    Written by

    Peter Whyte

  • HADR_LOGCAPTURE_WAIT Wait Type in SQL Server

    ⏳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…

    Written by

    Peter Whyte

  • HADR_ARCONTROLLER and HADR_FILESTREAM_IOMGR Wait Types in SQL Server

    ⏳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,…

    Written by

    Peter Whyte

  • DBA Scripts: Get Temp DB Hotspots

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    🔧Part of the DBA-Tools Project, copy/paste SQL Server scripts and health checks.In: Storage & Capacity Temp DB is shared by every database and every session on the instance: temp tables, table variables, sort and hash spills, version store for snapshot isolation, all of it lands in the same handful of files. When Temp DB is…

    Written by

    Peter Whyte

  • HADR_GROUP_COMMIT Wait Type in SQL Server

    ⏳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…

    Written by

    Peter Whyte

  • HADR_FILESTREAM_IOMGR_IOCOMPLETION Wait Type in SQL Server

    ⏳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…

    Written by

    Peter Whyte
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