AIX

Hi Folks,

Currently we are having the below configuration in one of our AIX 6.1 server.

RAM:- 8 GB
Paging space :- 19 GB
CPU processor:- 1
CPU type: 64 bit

But we would like to upgrade the configuration to below to improve the system performance and resolve some memory issues.

RAM:- 32 GB
paging space: 40 GB
CPU processor :-1

Could you please confirm and let us know the below points.?

1.) Is This configuraion is with 1 CPU processor will be possible.?
2.) Can we see any perfomance with 1 CPU core or any impact?
3.) There will be any limitation in CPU core if we upgrade the RAM to 32 GB?

~Have a Good Day

Thank You,
Suman B

Do you have any hard coded facts and figures to show the memory problem!

One cannot just provide feed back with so little info, can you clarify the below
- Are you seeing the error logs in error report?
- Is the system hanging?
- What is running on the system? what kind of server is it? like DB or Application.
- What kind of DB (oracle, db2) or what is the application?
- Since when are you seeing this problem?

Why so much paging space?

As a workaround this will work for some time, but the issue why you have memory problems might still show up, can just take longer until the RAM is used up. But that depends on what you are running and how the problems shows itself.
Though additional CPU units will not help with memory issues.

So as the others suggested, you should investigate what is the reason for your memory problem.

And as blackrageous asked, there is no need for so much paging space. I would go for a fix Paging Space size of 5GB or 10GB. When your system starts to use it, the performance will usually degrade enormous and so the goal is to avoid that before it happens.

- Are you seeing the error logs in error report?
Out of Memory Errors in the logs. Jobs are getting failed due to this.

- Is the system hanging?
The system is slow when the memory levels reaching to 99%

- What is running on the system? what kind of server is it? like DB or Application.
Application

- What kind of DB (oracle, db2) or what is the application?
DB2

- Since when are you seeing this problem?
When the application goes on live

If it the out of memory occurs directly after the application or DB2 is started, you might want to check, to which value the parameter database_memory is set, or maybe one of the other memory parameter for DB2.

Trivia:
IBM DB2 9.5 Information Center for Linux, UNIX, and Windows

How to do check:
IBM DB2 9.5 Information Center for Linux, UNIX, and Windows

When it occurs, just to make sure, use svmon -P | grep -p Pid to determin which is using Paging Space. You will simply see it, when there is not a null in the column "Pgsp" to find the culprit.

So it could be, that you overcommit memory to the database, that you don't even have (in the old setup) as physical RAM available.

Another thing comes to my mind - has your OS been "tuned"? Maybe post the output of vmo -F -L lru_file_repage -L minperm% -L maxperm% -L maxclient% -L maxpin%.

I would not worry about real memory reporting 99% with vmstat, nmon or such like, as AIX keeps real memory even when a process ends just in case the same data is needed later. You need to keep an eye on paging to see if you are really running out of real memory.

Code:

lsps -a

You also need to consider if your DB has a real-memory requirement. If you exceed the real memory, you system will start to page. Check vmstat for the pi & po columns to see read and writes to/from disks for paging.

If your DB requires (or is set for) large real memory, then that can be a problem too. This is an allocation that is not eligible for paging. if you run multiple instances, remember that they will each want their own allocation and that you may be exceeding the machine limits there. The settings in the DB startup parameters is not defining how big a machine you have, it's how much you are allocating to that instance - a mistake we have seen here.



I hope that these help,
Robin