Occurs when waiting for an UP (update) latch. This does not include buffer latches or transaction mark latches.
Latches are lightweight, fast methods of managing concurrency on a specific resource. This group of latches are seen in management of pages that have already been read into memory.
Books online says "Occurs when waiting for an UP (update) latch. This does not include buffer latches or transaction mark latches. A listing of
LATCH_* waits is available in
sys.dm_os_latch_stats. Note that
LATCH_DT waits together".
How to reduce this wait
There is a great article in sqlskills.com under the LATCH_EX page which gives a breakdown of the steps needed to identify the latch which you are waiting on - as although the wait time is shown, it does not identify the specific latch being contended for.
- Microsoft Docs - sys.dm_os_wait_stats (Transact-SQL)
- sqlskills.com - LATCH_SH
- sqlshack.com - All about latches
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