[blpower]

We just installed a new Oracle 10 Rac environment using to P550 serves with 8 gig of Ram. We have two internal disks mirrored and the rest are IBM DS4800 SAN disks. We currently have 6 databases in the rac environment. Problem we are having is that everytime we run a copy command or zip command we start paging. Hdisk0 and Hdisk1 go up to 100%. I was wondering a few things.

1. Should paging space be mirrored ?
2. If anyone has had this problem with Rac environment and what vio parameters did they use to maybe better tune the environment.
3. Just wondering if we put the OS disk on the SAN would it make difference.

Any help is appreciated Thanks

[cdelgadop]

Hi

1- Yes, it should be mirrored. Some people just don't mirror and just in case of disaster they go and create and activate a second mirror in the surviving disk. I usually create just one mirror on hdisk0 and mirror to the second rootvg disk. Mirroring at AIX LVM level is costly so you have to tune your Virtual Memory Manager (VMM) subsystem in such a way paging is avoided. You need to config the following parameters:

maxperm
minperm
maxclient

You can see the current values by running:

vmo -a | egrep "maxperm|minperm|maxclient"

By default they are 80/20/80. SAP, Oracle, DB2, Sybase, Lotus Domino, and personal experience recommends the following values:

maxperm = 08
minperm = 03
maxclient = 08

There're 2 new values (lru related) that changed these values.

2- Yes i have had these problems and solved the way proposed. Modifyng vMM parameters. Please check Oracle documentation.

3- Hmmm. I don't think so. Your goal should be less paging space as possible. UNIX servers running with more than 25% of paging have performance problems.

Hope this helps

[blpower]

Thanks for your help, I'm playing with the setting in my test envornment an it shows very promising results. I did talk with IBM they recommented setting the parameters:

20
5
20

But I didn't really like the results so I switched back to your setttings.

Thanks for the help

[Frans]

I also think you need to add more memory and tune oracle
there is a redbook on Oracle best practice for AIX

Also make sure that system layout is for best performance Oracle should have its own disks , Do not make paging to big

[blpower]

I found that this seems to be only happening when we used RMAN writing from asm to a filesystem. I implemented CIO option on the filesystem and this seems to have fixed the problem. What I think is happening is that RMAN using a block size that is to small to write to the filesystem granted I don't know what rman is doing underneath the covers but I think it thinks that it is writing to a raw partition instead of a filesystem. When I did a dd command to the filesystem using a block size of 256 I got the same results. After implementing CIO everthing was fine.