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LATCH_UP

Short Description

Occurs when waiting for an UP (update) latch. This does not include buffer latches or transaction mark latches.

Detailed Description

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 sys.dm_os_latch_stats groups LATCH_NL, LATCH_SH, LATCH_UP, LATCH_EX, and 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.

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