Computational Vs Non Computational

[night100781]

Hi all,

I've been to a course last year regarding AIX performance but i'm still confused between those two terms! I know that the VMM is considered to be Real Memory + physical Memory. The physical part of the memory is divided into three parts: presistent file system, persistent clint pages and paging space!

Bottom line, i'm having a system running oracle 10g application and the (computational) memory in that system is showing 83% when viewed using topas. What does that mean? and how can i relate this to what i understood above?

Regards,
Night

 

[hfaix]

I would say it most likely means you have lots of users sessions (PGA) and a relatively large sga (in comparision to total physical RAM).

My experience (learned the hard way) says the jobs will start failing around 96% Computational. Oracle doesn't seem to want to page.

You could run:

ps vg |sort -rn +6
svmon -Put 5 (top 5 users or ram)
svmon -G
or nmon

to see where your ram is being used.

 

[kHz]

Persistant segments = data files and executable program text.
Working segments = tranistory and can be shared libraries, etc.

Computational pages are working segments.

Generally, for databases you don't want to do double buffering (caching) because the database does that itself. Therefore you want to have minperm maybe at 5% and maxperm at 30% and maxclient equal to maxperm.

Those are just suggestions and you need to determine what works best for you.

You can also check your memory for overcomitment. Check this by using avm vs. real memory. Also check for ((sum of po/5 / sum of fr/5)) > 17% and there is a problem.

There may be little room for memory tuning if you are at 83% (maybe a little); depending on if avm is greater or less than real memory.

If so, then real memory is only cure.

 

[night100781]

Thank you hfaix & kHz for the nice comments.

I'm not at work for now and I won't be till next year coz I just had a baby

But i will try your recommendations once i get back to work

hfaix, sorry if i said what do you mean by sga and pga? as you know i'm new to all of this stuff so could you please explain it in plain English

Cheers

 

[khalidaaa]

Hi Night, See if this helps.

VMM - is the virtual memory manager, a process that is part of the kernel
and is responsible for managing
memory.

Virtual memory is real memory plus disk space (both addresses to data on
disks and paging space)

Non-Computational memory pages are pages of real memory that contain data
that has a persistent location
on disk (executable code of a command, data from a file, etc. not from
data stored in paging space).

Computational memory pages are pages of real memory that do not have a
persistent location on disk, they
are pages of memory needed by a process when it is started and no longer
available when the process
terminates. These are pages in memory that contain things like process
stack and heap, and malloced
space. When memory becomes over committed these pages need to be stored
someplace temporarily
and that is on paging space.