Disable Lock Escalation in SQL Server

Posted in: Technical Track

If a lot of rows or pages are locked, the SQL Server escalates to a table-level lock, to save resources. Each single lock takes approx. 100 bytes. So if you have many locks it takes a lot of resources to manage them. (There is a great blog about lock escalation, if you want some more info: https://blogs.msdn.com/b/sqlserverstorageengine/archive/2006/05/17/lock-escalation.aspx)

 

Until SQL Server 2008, there was no way to change the lock escalation for a single table. You could deactivate the escalation for the server by using the Trace Flags:

  • 1211 – Disables Lock Escalation completely – allows to use 60% of the allocated memory – if 60% of memory is used and more locking is needed you will get an out-of-memory error.
  • 1224 – Disables Lock Escalation until the memory threshold of 40% allocated memory is reached – after that Lock Escalation is enabled.

 

But that was in most cases not a good choice and caused a lot of performance problems. In SQL-Server 2008 and above there is a new table option (ALTER-TABLE) that can be used to change the default Lock-Escalation. This helps you if you have a table where you want to disable the escalation or if the table is partitioned.

 

On a partitioned table activating the AUTO Option can improve concurrency, by escalating the locks to the partition-level and not to the table-level.

ALTER TABLE – table option:

SET ( LOCK_ESCALATION = { AUTO | TABLE | DISABLE } )

  • AUTO (should be considered if you have a partitioned table)
  • If tables is partitioned – the locks will be escalated to the partition-level
  • If table is not partitioned – the locks will be escalated to the table-level
  • TABLE
  • Default behavior
  • Locks are escalated to the table-level
  • DISABLE
  • Lock escalation to the table-level is deactivated in most cases
  • In some necessary cases it’s allowed to escalate to the table-level

This is a cool feature, that are many developers are not aware of.

Thanks for Reading!

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