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Virtual Memory (confusion)

shikhar_1
Regular Advisor

Virtual Memory (confusion)

Hi,

 

I have some confusion about the VM memory and swap and psuedo memory.

Below are details for my server:

 

Total VM :  61.1gb   Sys Mem  :  30.7gb   User Mem:  54.7gb   Phys Mem : 191.8gb
Active VM:  17.5gb   Buf Cache:     1mb   Free Mem: 102.8gb   FileCache:   3.6gb

 

I would be interested to understand why the database sever is using virtual memory when there is plenty of free physical memory.

 

Please reply.

3 REPLIES
Dennis Handly
Acclaimed Contributor

Re: Virtual Memory (confusion)

>I have some confusion about the VM memory and swap and pseudo memory.

 

Virtual Memory is the overall term for RAM or swap.  The CPU typically loads from virtual addresses which are mapped to physical addresses, possibly with page outs and page ins using swap.

 

To check your swap usage, use "swapinfo -tam" and vmstat.

shikhar_1
Regular Advisor

Re: Virtual Memory (confusion)

Thanks for your reply.

 

As I can see on the server using glance that around 61 GB is showing for VM and some space for Active VM. How the server is defining this space?

Dennis Handly
Acclaimed Contributor

Re: Virtual Memory (confusion)

>How the server is defining this space?

 

VM includes both swap and RAM.  You need to look for glance stats on swapping.