Things to check

[coral09]

can anyone guide what are things to check whether I add more RAM to Aix server box or not

Thanks in advance

 

[khalidaaa]

Nice link:

http://www.tek-tips.com/viewthread.cfm?qid=1446162&page=1

Regards,
Khalid

 

[khalidaaa]

That's what IBM says about that in their performance manaual:

[b]Page ins and page outs[/b]
When determining if a system may be short on memory or if some memory tuning needs to be done, run the vmstat command over a set interval and examine the pi and po columns. These columns indicate the number of paging space page-ins/per second and the number of paging space page-outs/per second. If the values are constantly non-zero, there is most likely a memory bottleneck. Occasional non-zero values don’t necessarily indicate a problem since paging is the main principle of virtual memory.
Notice the high I/O wait in the output and also the number of threads on the blocked queue. The I/O is likely due to the paging in/out from paging space.

[b]Determining if there is enough RAM[/b]
One way to determine the appropriate amount of RAM for a system is to look at the largest value for avm as reported by vmstat. Multiply that by 4 KB to get the number of bytes and then compare that to the number of bytes of RAM in the system. Ideally, avm should be smaller than total RAM. If not, some amount of virtual memory paging will occur. How much will depend on the difference between the two values. Remember, the idea of virtual memory is that it gives us the capability of addressing more memory than
we have (some of the memory is in RAM and the rest is in paging space). But, if there is far more virtual memory than real memory, this could cause excessive paging which
then results in delays. If avm is lower than RAM, then paging space paging could be caused by RAM being filled up with file pages. In that case, tuning the minperm/maxperm values could reduce the amount of paging space paging.
As a rule of thumb, memory is over committed if (%avm + 5%) > 100%
where:
%avm=(avm*4096/RAM installed)*100
The value for RAM installed can be found with the bootinfo -r command.
(Note: this rule of thumb might not apply for database servers using raw logical volumes
instead of file systems).

Regards,
Khalid

 

[mrn]

The answer is always yes......

Are you using nmon, if not get it and the analyzer from here

http://www.ibm.com/developerworks/aix/library/au-analyze_aix/

Start collecting stats over a couple of weeks (or longer for better trend analasys) then use the analyzer, it'll give you some really useful graphs and indications.

Is your system tuned?
What Version of AIX?



Mike

"Whenever I dwell for any length of time on my own shortcomings, they gradually begin to seem mild, harmless, rather engaging little things, not at all like the staring defects in other people's characters."