How can I make sure that in RAM our sql server is not facing any mermory crunch issue?

Question

The SQL server process always show RAM is highly used while its a default behaviour of sql server.
How can I make sure that in RAM our sql server is not facing any mermory crunch issue?
Thanks

Answer 1

The SQL server process always show RAM is highly used while its a default behaviour of sql server.
How can I make sure that in RAM our sql server is not facing any mermory crunch issue?
Thanks
The best way to make sure you are not facing memory pressure is to use perfmon counters and monitor various memory counters
For SQL Server 2005 - 2008 r2 use below counters
SQLServer:Buffer Manager--Buffer Cache hit ratio(BCHR): IIf your BCHR is high 90 to 100 Then it points to fact that You don't have memory pressure. Keep in mind that suppose somebody runs a query which request large amount of pages in that
case momentarily BCHR might come down to 60 or 70 may be less but that does not means it is a memory pressure it means your query requires large memory and will take it. After that query completes you will see BCHR risiing again
SQLServer:Buffer Manager--Page Life Expectancy(PLE): PLE shows for how long page remain in buffer pool. The longer it stays the better it is. Its common misconception to take 300 as a baseline for PLE.   But it is not,I read it from
Jonathan Kehayias book( troubleshooting SQL Server) that this value was baseline when SQL Server was of 2000 version and max RAM one could see was from 4-6 G. Now with 200G or RAM coming into picture this value is not correct. He also gave the formula( tentative)
how to calculate it. Take the base counter value of 300 presented by most resources, and then determine a multiple of this value based on the configured buffer cache size, which is the 'max server memory' sp_ configure option in SQL Server, divided by 4 GB.
  So, for a server with 32 GB allocated to the buffer pool, the PLE value should be at least (32/4)*300 = 2400. So far this has done good to me so I would recommend you to use it.  
SQLServer:Buffer Manager--CheckpointPages/sec: Checkpoint pages /sec counter is important to know about memory pressure because if buffer cache is low then lots of new pages needs to be brought into and flushed out from buffer pool, 
due to load checkpoint's work will increase and will start flushing out dirty pages very frequently. If this counter is high then your SQL Server buffer pool is not able to cope up with requests coming and we need to increase it by increasing buffer pool memory
or by increasing physical RAM and then making adequate changes in Buffer pool size. Technically this value should be low if you are looking at line graph in perfmon this value should always touch base for stable system.  
SQLServer:Buffer Manager--Freepages: This value should not be less you always want to see high value for it.  
SQLServer:Memory Manager--Memory Grants Pending: If you see
memory grants pending in buffer pool your server is facing SQL Server memory crunch and increasing memory would be a good idea. For memory grants please read this article: 
SQLServer:memory Manager--Target Server Memory: This is amount of memory SQL Server is trying to acquire.
SQLServer:memory Manager--Total Server memory This is current memory SQL Server has acquired.
   8.  Free List Stalls/sec – Number of requests per second that had to wait for a free page
   9. Free Pages – Total number of pages on all free lists (free lists track all of the pages in the buffer pool that are not currently allocate to a data page, and are therefore available for usage immediately)
NOTE: If you have NUMA system don't use PLE to monitor memory condition it wont give correct value
From 2012 Onwards
Memory management has become easy from 2012 onwards as
Max server memory also allocated memory for requests which require memory >8KB
SQLServer:Memory Manager:Free Memory (KB)
SQLServer:Memory Manager:Target Server Memory (KB)
SQLServer:Memory Manager:Total Server Memory (KB)
For NUMA system its also wort monitoring each node.
Object - SQLServer:Memory Node:Total Node Memory
  (KB)
Object - SQLServer:Memory Node:Target Node Memory
  (KB)
Object - SQLServer:Memory Node:Free Node Memory
  (KB)
Ideally if target server memory is less than or equal to total server memory there wont be memory pressure if target is > total it does not always means its memory pressure
BCHR would also give you good idea about memory pressure
If memory grants pending is frequently non zero there is memory pressure
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