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  • MSQL_DQ Wait Type in SQL Server

    ⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: ASYNC_NETWORK_IO Wait TypeRelated pillar: Performance & Troubleshooting Is It a Problem? It is honest accounting of remote time, so it matters as much as your workload depends on distributed queries. Sustained, it means sessions spend real time waiting on a remote…

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  • METADATA_LAZYCACHE_RWLOCK 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 Is It a Problem? Not on any current version, because it does not exist there. Microsoft lists it as internal use only and applying to SQL Server 2008 R2 only. Get Wait Statistics does…

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  • MEMORY_ALLOCATION_EXT Wait Type in SQL Server

    ⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: RESOURCE_SEMAPHORE Wait TypeRelated pillar: Performance & Troubleshooting Is It a Problem? Almost never. Get Wait Statistics filters it out by default, and its source notes it as millions of microsecond waits on every instance. Our SQL Server 2025 lab: about 56…

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  • LOGPOOL Wait Types in SQL Server

    ⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: WRITELOG Wait TypeRelated pillar: Performance & Troubleshooting The LOGPOOL_* waits belong to one structure, and this page covers them together: LOGPOOL_CACHESIZE, LOGPOOL_CONSUMER, LOGPOOL_CONSUMERSET, LOGPOOL_FREEPOOLS and LOGPOOL_REPLACEMENTSET. Microsoft lists all five as internal use only, from SQL Server 2012. The log pool…

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  • LOGMGR_RESERVE_APPEND Wait Type in SQL Server

    ⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: WRITELOG Wait TypeRelated pillar: Performance & Troubleshooting ⚡LOGMGR_RESERVE_APPEND means a transaction log ran out of room: a session needed to write a log record, the log could not grow, and it is waiting to see whether truncation frees space. It is…

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  • DBA Scripts: Get Blocking Summary

    🔧Part of the DBA-Tools Project, copy/paste SQL Server scripts and health checks.In: Performance & Troubleshooting › Blocking & Locking When Everything Looks Busy But Nothing Is Moving Blocking is one of the most common causes of a SQL Server that suddenly looks frozen. Applications start timing out, users report that everything has stopped responding, and…

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  • LOGMGR_QUEUE Wait Type in SQL Server

    ⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: WRITELOG Wait TypeRelated pillar: Performance & Troubleshooting Is It a Problem? No. It is one of the best-known benign waits, commonly filtered, and Get Wait Statistics filters it out by default. It sits near the top of raw output on almost…

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  • LOGMGR Wait Type in SQL Server

    ⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: WRITELOG Wait TypeRelated pillar: Performance & Troubleshooting Is It a Problem? Almost never in a normal wait profile, because databases do not usually close while the instance is running; it was zero on our SQL Server 2025 lab. Get Wait Statistics…

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  • LCK_M_SIX Wait Type in SQL Server

    ⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: LCK_M_X, LCK_M_S, and LCK_M_U Wait TypesRelated pillar: Performance & Troubleshooting ⚡LCK_M_SIX is a transaction waiting for a table-wide lock that lets it read the whole table while changing some of it. It is rare, so any amount points at one transaction…

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  • LCK_M_SCH_S Wait Type in SQL Server

    ⏳Part of the SQL Server Wait Types Library, every wait type explained.Related deep dive: LCK_M_X, LCK_M_S, and LCK_M_U Wait TypesRelated pillar: Performance & Troubleshooting ⚡LCK_M_SCH_S means queries cannot even start on a table, because DDL holds or is queued for a schema modification lock on it. One stuck ALTER or offline rebuild can stall every…

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