I wonder why SQL Server does not use all available memory - 100% when I am quite sure there is a memory bottleneck. For example, one server I administer starts with using 91% of memory and gradually increases up to 98 but not 100. Increase trend is as follows after a restart at 23:00:
- 58% after restart and reaches 79% throughout the night. I suppose this should be due to overnight back-ups taken.
- 82% by 11:00 next day.
- 90% by 12:00
- A steady trend throughout the day until 23:00 when memory utilization increases to 93%
- 95% next morning at 08:00
- 97% at 17:00
- 98% next day at 14:00 and stays there.
What might be causing that 2% not being utilized? Is it possible that Windows O/S is preventing it? If so, how can I prove that indeed Windows is keeping it to itself?
I am referring to the overall memory usage by the server - i.e the OS. Max memory configuration is already set well beyond the server's current memory. I have a monitoring tool at hand for tracking memory utilization.
Memory utilization by the server is no less nor above 98%. This is a dedicated, single-instance, two database SQL Server on which no other services, applications etc. are running. SQL Server might be using most of the allocated memory -i.e. 98%- but my question is why is it not using the rest 2%? I'm not sure if I am becoming too peevish in questioning that 2%?
Thanks to the query Determining Current Memory Allocation in Monitor memory usage I confirm Memory_usedby_Sqlserver_GB is 60 out of 64 GB total RAM. I was unable to find the column for
max server memory and total RAM in the output of
sys.dm_os_process_memory DMV (maybe due to SQL Server 2008 R2) but I may confirm it is a 64 GB server and max. server memory is set to 2147483647 MB.
I don't know if my server will utilize any extra memory once they are put in the slots. I am trying to prove if the server needs more memory, (if so) will make use of it and thus make a cause to push for purchase. I will be left in an awkward position if the memory is bought and memory utilization does not increase and stays in its current state - 60 GB. Seeing 60 GB of RAM being utilized after increasing the server's memory from 64 GB to 128 GB will be a waste of money.I want to make sure before the fact if the server will benefit from the new extra RAMs or be indifferent.