Re: Keeping an Oracle 8.1.7 SGA in Physical Memory on Solaris 8

From: Pete Finnigan <pete_at_peterfinnigan.demon.co.uk>
Date: Fri, 31 Aug 2001 09:49:08 +0100
Message-ID: <973KGJAE+0j7EwJF@peterfinnigan.demon.co.uk>

Hi

I have done this before. LOCK_SGA does not work on solaris unless you run the Oracle exe as root, as no one but root can lock shared memory segments. Use_ism did not use to work correctly , not sure what version of oracle, support told us to turn it off at one point. use_ism is not the same as locking shared memory segments in core though.

If you are looking to lock shared memory i take it you are having paging issues. Check vmstat and search on google or whatever to read about priority paging and what are real page in's and outs.

You should also look at the "priority paging" mechanism used in solaris.

add the parameter priority_paging=1 to your /etc/system This will stop the kernel grabbing all the free kernel memory.

To lock the sga in core you need a simple C program as follows

#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <errno.h>

main(int argc,char **argv)
{

        int sh;
        int result;

        sh=atol(argv[1]);
        printf("locking id %d into core\n",sh);
        result=shmctl(sh,SHM_LOCK,(struct shmid_ds *)0);
        if (result==0)
        {
                printf("Locked successfully\n");
        }
        else
        {
                perror("Failed to lock");
        }

}

Then you can call it for each shared memory segment owned by oarcle after the instance has been started, using

ipcs -m.

you can put this in a loop and grep for oracle and call the compiled C program and run it automatically on startup.

We fixed a major memory issue with priority paging and locking the core

I hope this helps

cheers

Pete Finnigan
www.pentest-limited.com

In article <20010830.17082600_at_its.charlestoncounty.org>, Peter Shankey <shankeyp_at_its.charlestoncounty.org> writes
>Oracle has an parameter called LOCK_SGA which will lock the memory the
>SGA uses into physical memory. I saw a tech note on metalink.oracle.com
>but it applied to HPUX. The error I get on Solaris is:
>
>Connected to:
>Oracle8i Enterprise Edition Release 8.1.7.0.0 - Production
>With the Partitioning option
>JServer Release 8.1.7.0.0 - Production
>
>SQL> shutdown immediate
>Database closed.
>Database dismounted.
>ORACLE instance shut down.
>SQL> startup
>ORA-27126: unable to lock shared memory segment in core
>SVR4 Error: 1: Not owner
>SQL>
>
>My question is how do or can I configure the OS to do this, and has
>anyone had bad experiences doing this?
>
>My situation is I have a couple of test Oracle instances and a couple of
>product one. I want the production instances to get the memory.
>Unfortunately I am maxed on memory.
>
>Pete

-- 
Pete Finnigan
IT Security Consultant
PenTest Limited

Office  01565 830 990
Fax     01565 830 889
Mobile  07974 087 885

pete.finnigan_at_pentest-limited.com

www.pentest-limited.com

Received on Fri Aug 31 2001 - 03:49:08 CDT