Physical Memory: 97%

Question

I have a SQL Server 2008 R2 on Windows Server 2008 R2, on 64-bit virtual machine, dual processors dual quad core , and 32 GB RAM.
If I restart the server, and after all the processes and services start running, the used memory is not more than 4 ~ 6 GB (I don't remember exactly, but small compared to the overall 32 GB). Every day the used memory increases for 2~3 GB!, till it reaches
97% of the physical memory (31 GB),  29 GB of them for the SQL Server:
My question is how can I know what SQL Server processes or queries causes those increases in the memory? and if it is a process or query, why the used memory is not released after that process or query finishes ?!
Honestly, there is no complain about the performance of the server, but the weird thing is that as much as I give the server RAM as much as the SQL Server takes! The server was 8 GB and I increased it to 16 then 32 GB, but the SQL Server keeps eating more
and more!

Answer 1

Hi,
>>If I restart the server, and after all the processes and services start running, the used memory is not more than 4 ~ 6 GB (I don't remember exactly, but small compared to the overall 32 GB). Every day the used memory increases for 2~3 GB!,
till it reaches 97%
This is the way SQL Server memory works.When you restarted it its usage was low slowly you started running complex queries on SQL server which required pages from disk now SQL server started bringing these pages from disk into memory to make sure your query
is satisfied .Now when second time you use same query it will be fast as comapared to previous attempt as now there is no use of bringing pages in memory .Now if SQL would have released memory back your time taken would have been same and you would complain
about query being slow.This is the reaosn SQL caches as much data page it can so as to satify query from meory not picking pages from disk which is costly.But if Os faces presasure and SQLOS asks SQL server to trim its memory consuption it will do it politely.So
please dont be alarmed with SQL server using memory.
PLease dont look at task manager for SQL server memory consumption it might not show you correct memory utilization .I always recommend below DMV
select
(physical_memory_in_use_kb/1024)Memory_usedby_Sqlserver_MB,
(locked_page_allocations_kb/1024 )Locked_pages_used_Sqlserver_MB,
(total_virtual_address_space_kb/1024 )Total_VAS_in_MB,
process_physical_memory_low,
process_virtual_memory_low
from sys. dm_os_process_memory
If you do not want SQL server to use much memory you can change it from sp_configure by setting lower value for max server memory.But I am in favour you shoudl not do that .Set an optimum value for max server memory leaving 7-8 G for OS and other processes
running.
>>My question is how can I know what SQL Server processes or queries causes those increases in the memory?
I have never tried that and its little difficult to find what process unless that process is runnin.There is DMV sys.dm_os_buffer_descriptor which will tell you which database is using how much memory.Below query will resturn count of page loaded by each
database
http://technet.microsoft.com/en-us/library/ms173442.aspx
SELECT COUNT(*)AS cached_pages_count
,CASE database_id
WHEN 32767 THEN 'ResourceDb'
ELSE db_name(database_id)
END AS database_name
FROM sys.dm_os_buffer_descriptors
GROUP BY db_name(database_id) ,database_id
ORDER BY cached_pages_count DESC;
For further reading about memory to know that its really a normal behavior please see
Basics of memory
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