Category: Wait Types

  • PAGEIOLATCH_SH Wait Type in SQL Server

    ⏳Part of the SQL Server Wait Types Library, every wait type explained.Related pillar: Storage & Capacity PAGEIOLATCH_SH appears when a query needs a data page that is not in the buffer pool, so SQL Server must read it from disk. The SH stands for shared latch, the read operation. The query waits until the I/O…

    Written by

    Peter Whyte

  • ASYNC_NETWORK_IO Wait Type in SQL Server

    ⏳Part of the SQL Server Wait Types Library, every wait type explained.Related pillar: Performance & Troubleshooting ASYNC_NETWORK_IO appears when SQL Server has finished producing rows and is waiting for the client application to read them from the network buffer. SQL Server filled its output buffer, the client hasn’t acknowledged it yet, and SQL Server is…

    Written by

    Peter Whyte

  • PAGELATCH_EX Wait Type in SQL Server

    ⏳Part of the SQL Server Wait Types Library, every wait type explained.Related pillar: Performance & Troubleshooting PAGELATCH_EX (and its sibling PAGELATCH_UP) is a latch wait on a page that is already in memory. That one word, memory, is the whole story. This is not disk I/O. If you see PAGE**IO**LATCH you have a storage problem;…

    Written by

    Peter Whyte

  • AM_INDBUILD_ALLOCATION and AM_SCHEMAMGR_UNSHARED_CACHE Wait Types in SQL Server

    ⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: IO_COMPLETION Wait TypeRelated pillar: Performance & Troubleshooting Two Access Methods (AM) waits share this page: AM_INDBUILD_ALLOCATION: a thread waiting for exclusive access to an extent during allocations while building or rebuilding indexes. Parallel index builds allocate space aggressively, and workers occasionally…

    Written by

    Peter Whyte

  • WAITFOR Wait Type in SQL Server

    ⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: SOS_SCHEDULER_YIELD Wait TypeRelated pillar: Performance & Troubleshooting WAITFOR is the most literal wait type in the DMV: it records sessions executing a WAITFOR DELAY or WAITFOR TIME statement. The duration is exactly what the T-SQL asked for. Nothing is contended and…

    Written by

    Peter Whyte

  • BACKUP Wait Type in SQL Server

    ⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: BACKUPIO and BACKUPBUFFER Wait TypesRelated pillar: Backup & Recovery BACKUP is recorded when a thread involved in backup processing waits to synchronise with the other threads of the same backup. Backups run as a multi-threaded pipeline (readers, writers, a coordinator), and…

    Written by

    Peter Whyte

  • BACKUPTHREAD Wait Type in SQL Server

    ⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: BACKUPIO and BACKUPBUFFER Wait TypesRelated pillar: Backup & Recovery BACKUPTHREAD is recorded when a thread involved in a backup or restore waits for other threads in the same operation to finish their part. Backups are multi-threaded pipelines, readers pulling pages, writers…

    Written by

    Peter Whyte

  • BAD_PAGE_PROCESS Wait Type in SQL Server

    ⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: PAGEIOLATCH_SH Wait TypeRelated pillar: Performance & Troubleshooting BAD_PAGE_PROCESS is recorded by the background suspect page logger, the process that records 823 and 824 I/O errors into msdb.dbo.suspect_pages, as it throttles itself to run no more than once every five seconds. You…

    Written by

    Peter Whyte

  • BROKER_TASK_STOP Wait Type in SQL Server

    ⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: SOS_SCHEDULER_YIELD Wait TypeRelated pillar: Performance & Troubleshooting BROKER_TASK_STOP is recorded when a Service Broker internal task handler waits (up to ten seconds at a time) to shut itself down because there are no Broker tasks, message transmission, receipt, or other asynchronous…

    Written by

    Peter Whyte

  • BROKER_TO_FLUSH Wait Type in SQL Server

    ⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: SOS_SCHEDULER_YIELD Wait TypeRelated pillar: Performance & Troubleshooting BROKER_TO_FLUSH is recorded by the Service Broker lazy flusher, the background thread that writes inactive transmission objects (the structures tracking message transmissions per dialog) out to a tempdb worktable to save memory. The detail…

    Written by

    Peter Whyte
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