I've been asked to look at setting an Oracle SGA of over 2Gb on an 8400 with
8Gb running DU4.0d. There appear to be two possibles here. One is to
increase shm-max to the largest SGA size, say 3Gb, the other is to dabble
with the gh-chunks shared memory enhancements and place the SGA outside of
VM system control. There appears to be some advantages in doing the latter,
ref article:
http://www.ornl.gov/its/archives/mailing-lists/alpha-osf-managers/1997/08/ms
g00440.html (specifically the entry from Peter Flack)
The System Config and Tuning manual states that the maximum value for
shm-max is 2Gb minus 8Mb (system V shared memory segment limitation),
therefore this blows away possibility number one listed above! So does this
mean that if I don't use gh-chunks I can't have an SGA of 2Gb plus? Or does
it mean I can, but it's in multiple segments?
If I have to use gh-chunks to set a 3Gb SGA, does the following sound about
right?
shm-max=536870912 (512Mb)
gh-chunks=768 (768 x 4Mb = 3Gb)
shm-mni=128 (default value)
msg-mni=2048 (previously set value)
shm-seg=1024 (previously set value)
Do I need to set ssm-threshold to 0? Also, are there any other specifics
that the Oracle DBAs need to do to use this shared memory or will it
automatically get used?
Dave Campbell
Vodafone Ltd.
e-mail : dave.campbell_at_vf.vodafone.co.uk
Quote of the day:
If at first you don't succeed, then skydiving definitely is not the sport
for you.
Received on Fri Apr 09 1999 - 09:17:46 NZST