More committed than physical memory, how is that possible?

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Question :

This is on SQL Server 2019, running on Windows 10 with 64GB or RAM. Trying to solve a memory issue I found a post where the following query was used:


SELECT virtual_address_space_reserved_kb as Reserved, 
       virtual_address_space_committed_kb Committed,
       physical_memory_in_use_kb as Physical
FROM sys.dm_os_process_memory 

Running the query on my server produced the following result:


Reserved     Committed   Physical

101,881,000  3,123,124   2,747,764

So committed memory was more than physical memory. I thought that was strange, so I restarted the server, run the query again and the numbers changed but Committed was still greater than Physical:


Reserved     Committed   Physical

102,000,616  2,259,624   1,743,392

Is that normal? If not, is there something horribly wrong with my server?

Answer :

So committed memory was more than physical memory. […] Is that normal? If not, is there something horribly wrong with my server?

Is it normal, yes. This has to do with the way the Windows Memory Manager works and the difference between committed and in physical memory (the memory model used here is to use virtual memory which allows for various ranges of storage for “memory” such as a page file or multiple page files). There is a superuser answer on this, additionally there is some decent reading about commit charge.

Memory can be a very large black hole, depending on how deep you want to go, but essentially not all memory is required to be in physical ram at all times (and can be paged out, which is a common term) depending on use (we’re only talking user-mode memory and not kernel). There are many facets to this, but nothing to worry about based on your output.

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