Author: Peter Whyte
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LCK_M_SCH_M 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_M is a wait to acquire a Schema Modification (SCH-M) lock. DDL needs this lock to change an object’s structure: ALTER TABLE, offline index rebuilds, partition switches, truncates, and drops all…
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LCK_M_RX_X 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_RX_X is a wait to acquire an Exclusive Range lock: an exclusive lock on a key value plus an exclusive lock on the range between it and the previous key. Like…
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LCK_M_RS_U 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_RS_U is a wait to acquire an Update lock on a key together with an Update Range lock on the gap between it and the previous key. It belongs to the…
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LCK_M_RS_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_RS_S is a wait to acquire a Range Shared lock: a shared lock on a key value plus a shared lock on the range between it and the previous key. Range…
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LCK_M_RIn_NL 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_RIn_NL is a wait to acquire an Insert Range lock with a NULL lock on the key itself. It appears when a session under SERIALIZABLE isolation wants to insert a new…
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LCK_M LOW_PRIORITY and ABORT_BLOCKERS Wait Types 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 Every lock mode in SQL Server has two extra wait type variants: LCK_M_<mode>_LOW_PRIORITY and LCK_M_<mode>_ABORT_BLOCKERS, 46 wait types in all (LCK_M_S_LOW_PRIORITY, LCK_M_SCH_M_ABORT_BLOCKERS, and so on). They exist for the WAIT_AT_LOW_PRIORITY option…
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LCK_M_IX 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_IX is a wait to acquire an Intent Exclusive (IX) lock. When SQL Server modifies a row, it first stamps IX locks on the page and table above it, signalling that…
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LCK_M_IS 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_IS is a wait to acquire an Intent Shared (IS) lock. Before SQL Server takes a shared lock on a row or page, it places IS locks on the table and…
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LAZYWRITER_SLEEP 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 LAZYWRITER_SLEEP is recorded by the lazy writer thread while it sleeps between checks of the buffer pool free list. Roughly once a second it wakes, checks whether memory pressure requires freeing buffers, does whatever…
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DBA Scripts: Get TempDB Configuration
🔧Part of the DBA-Tools Project, copy/paste SQL Server scripts and health checks.In: Storage & Capacity TempDB is shared by every database on the instance, and it’s usually the first thing to show contention under load, long before any user database does. Unlike a user database’s files, TempDB’s default configuration out of the box (a single…
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- Backups & Recovery (17)
- DBA Scripts (152)
- High Availability (HA) (13)
- Installation & Configuration (49)
- Maintenance (25)
- Migration & Upgrades (14)
- Monitoring (9)
- Performance Tuning (37)
- Security (Encryption & Permissions) (20)
- Storage & Capacity (16)
- T-SQL Fundamentals (15)
- Troubleshooting (94)
- Wait Types (235)