topic Virtual Memory (confusion) in Operating System - HP-UX

Virtual Memory (confusion)

shikhar_1 — Wed, 11 Sep 2013 14:34:04 GMT

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.

Re: Virtual Memory (confusion)

Dennis Handly — Wed, 11 Sep 2013 19:02:35 GMT

>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.

Re: Virtual Memory (confusion)

shikhar_1 — Thu, 12 Sep 2013 09:07:13 GMT

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?

Re: Virtual Memory (confusion)

Dennis Handly — Thu, 12 Sep 2013 22:19:20 GMT

>How the server is defining this space?

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