topic Re: Active Shared Memory Segments in Operating System - HP-UX

Active Shared Memory Segments

Shahul — Tue, 24 Apr 2007 03:48:13 GMT

Hi,

I am having trouble with one of the HP 11.11 server running with 5 oracle instances. The system's memory usage is growing everyday. It lookes like there are a lot of active shared memory segments not released when the oracle is restarted every night. Here is a sample of ipcs -m output. I can see many entries like this. Can someone tell me what could be the reason for this problem?

m 4106 0x00000000 --rw-rw---- oracle dba
m 4107 0x00000000 --rw-rw---- oracle dba
m 4108 0x00000000 --rw-rw---- oracle dba
m 4109 0x00000000 --rw-rw---- oracle dba
m 4110 0x00000000 --rw-rw---- oracle dba
m 4111 0x00000000 --rw-rw---- oracle dba
m 4112 0x00000000 --rw-rw---- oracle dba
m 4113 0x00000000 --rw-rw---- oracle dba
m 4114 0x00000000 --rw-rw---- oracle dba
m 4115 0x00000000 --rw-rw---- oracle dba

TIA
Shahul

Re: Active Shared Memory Segments

Steven E. Protter — Tue, 24 Apr 2007 04:15:07 GMT

Shalom Shahul,

Few things to look at:

1) kmtuune, you may be able to create more or larger segments to accomodate oracle.
2) Patching, the OS could have a memory leak issue. Latest bi-annual patch set is a good starting point. relink oracle after this.
3) Oracle patches. There are dozens of memory leak issues with each version of Oracle.

Normally, I avoid Oracle patches at all costs. However sometimes they can't be avoided.

SEP

Re: Active Shared Memory Segments

Steve Lewis — Tue, 24 Apr 2007 04:27:39 GMT

(a) why are you shutting it down every night?
(b) how are you shutting it down?
(c) how are you sure that it came down cleanly and removed all the attached shared memory segments when it did?

You must check thoroughly that the shutdown has worked.
Also check that you are not unnecessarily starting a duplicate service that was not stopped, which takes its own shared memory segment. Do an ipcs -ma and check the PIDs of these segments, then try to match them up with processes.

Re: Active Shared Memory Segments

Dennis Handly — Tue, 24 Apr 2007 04:50:03 GMT

Try "ipcs -ma" to get creation time, how many still attached and size.

>oracle is restarted every night.

If you don't do this properly, you would be responsible for cleaning up these shared memory segments with ipcrm(1).

Re: Active Shared Memory Segments

Bill Hassell — Tue, 24 Apr 2007 08:35:14 GMT

Actually, the definition a "active" is impossible to define. Only your application knows whether the segment is useful. Unlike a file, the data can be changed or accessed at any time by any application that knows the segment information. Oracle will release all segments when it is properly shutdown. If anyone is using kill -9, then segments will remain -- but more important, your database is being seriously corrupted by using kill -9. NEVER use kill -9 in a production system, especially for database applications.