LCK_M_X

Description

This wait occurs while a request is waiting to acquire an exclusive lock. It typically accumulates while requests are being blocked by a write transaction (implicit or explicit). When transactions are kept open for extended periods of time it can cause long delays for other requests

Resolved by

DBAs and Developers

Suggested solutions

  1. Keep transaction durations short.
  2. Ensure that transaction isolation levels are appropriate (avoid SERIALIZEABLE and REPEATABLE READ if possible)
  3. Investigate enabling the READ_COMMITTED_SNAPSHOT database setting
  4. Run trace/Profiler/Extended Event session in conjunction with Blocked Process Threshold to determine which queries are being blocked
  5. Indexing, ensure that long running queries and transactions are optimized
  6. Ensure that row, page and table locks are being escalated correctly. If the table is partitioned consider enabling partition escalation

Additional research

Reducing SQL Server Locks
Understanding Isolation Levels
Identify the Cause of SQL Server Blocking
Lock Escalations

See more

Consider using ApexSQL Monitor, a Windows and SQL Server monitoring tool able to track SQL Server wait types, including the individual query wait statistics

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