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shmmax !!!

Venky_1
Frequent Advisor

shmmax !!!

Hello,

I need information/clarification on the shmmax parameter. I would like to know what should be the ideal value of shmmax if I have physical memory of 10GB and Oracle processes being used
are highly memory intensive.

Please suggest....

Thanks ..
Venky
Winners never quit and quitters never win
9 REPLIES
Domenico_5
Respected Contributor

Re: shmmax !!!

another one

The shmmax 'Single shared memory segment' is limited to 1 GB (0x40000000)
on a 32-bit HP-UX 11.0 system. When running under the 64-bit operating
system, shmmax is limited to 1 TB (0x10000000000).

The maximum shared memory accessible (all segments/quadrants) is limited
to 2.75 GB on 32-bit, and 4 TB on 64-bit HP-UX systems.
Ravi_8
Honored Contributor

Re: shmmax !!!

Hi,

If you are any oracle, irrespective of RAM,
shmmax of 4GB is more enough
never give up
K.Vijayaragavan.
Respected Contributor

Re: shmmax !!!

Hi,

Check the docs at,

http://docs.hp.com/hpux/onlinedocs/os/KCparam.ShMmax.html

-K.Vijay
"Let us fine tune our knowledge together"
Sandip Ghosh
Honored Contributor

Re: shmmax !!!

What version of oracle you are using 32bit or 64 bit?

If you are using 64 bit then no problem But if you are using 32bit you have to use memory windows to increase the shared memory in Oracle.

Sandip
Good Luck!!!
Wodisch
Honored Contributor

Re: shmmax !!!

Hi,

if you have a system with 10GB of RAM, then you must be running HP-UX11 with 64bit kernel, anyway.
And then a 32bit Oracle make almost never sense IMHO.
So if you are left with 64bit everywhere you just have to care that nobody resets the value of SHMMAX to something smaller than your (free) RAM-size...

Just my $0.02,
Wodisch
Ross Martin
Trusted Contributor

Re: shmmax !!!

If you have 11.11, (aka. 11i) then you may have a problem increasing shmmax beyond 1GB.

This is a known problem.

The fix is to patch with PHKL_24032.

Hope that helps.

Ross Martin
Ross Martin
Trusted Contributor

Re: shmmax !!!

Here is a workaround if you can't access the patch:

The maximum value for shmmax for a 32-bit application is 1 Gb (0x40000000). But
since the maximum for a shared memory segment for a 64-bit application is 4
Terabytes, the following correction can be made to allow this:

1. Edit /usr/conf/master.d/sysv-shm and change:

*range shmmax<=0x40000000
To:
*range shmmax<=0x40000000000

2. Run '/usr/sam/lbin/getkinfo -b'
3. Use SAM to make the desired changed to shmmax


Ross Martin
UNIXTEK
Frequent Advisor

Re: shmmax !!!

Unless you have an enormous database,
set :
shmmax and maxdsiz_64bit to 4GB,
maxdsiz to 1 GB
maxtsiz to 1 GB

My experience tells me that the system
performs best when shmmax and maxdsiz_64bit
are equal.
Andreas D. Skjervold
Honored Contributor

Re: shmmax !!!

Hi

Just pump it up to your amount of physical RAM, ie 10GB.

This means just that the largest allowable memory segment is 10GB.
What you'll end up using for your Oracle SGA is a different story. This is dependent on the init.ora settings.

Andreas
Only by ignoring what everyone think is important, can you be aware of what everyone ignores!