Memory clerks DMV showing memory usage greater than server RAM

• Graham4th

  SSC-Addicted

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  January 28, 2021 at 5:45 pm

  #3838454

  Hi.

  This is probably a simple question for those in the know...

  I have a VM with 128GB of RAM installed and a single SQL Instance installed, with max server memory configuration set to 115GB.

  However when I query the sys.dm_os_memory_clerks DMV with the following query, the top two results add up to more than total server RAM on their own:

  select TOP 2 type, name, pages_kb / 1048576 AS [MemoryGB] from sys.dm_os_memory_clerks order by pages_kb desc

  MEMORYCLERK_SQLBUFFERPOOL - Default - 109

  MEMORYCLERK_SQLQERESERVATIONS - Default - 21

  Is this DMV meant to include just current physical RAM usage, or also pages swapped out to the page file (or elsewhere)?

  If the former, then it seems to be using more RAM than even the server has installed (never mind more than is configured), if the latter then this doesn't quite tally with the MS documentation on their Memory Management Architecture Guide page, where under the Dynamic Memory Management section it states:

  "Max server memory controls the SQL Server memory allocation, compile memory, all caches (including the buffer pool), query execution memory grants, lock manager memory, and CLR1 memory (essentially any memory clerk found in sys.dm_os_memory_clerks)."

   

  This isn't actually causing any issues for us at the moment, but I was curious to just understand what this meant.

  Thanks in advance!

• Site Owners

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  January 29, 2021 at 6:10 pm

  #3838844

  Thanks for posting your issue and hopefully someone will answer soon.

  This is an automated bump to increase visibility of your question.