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тАО06-06-2006 04:26 AM
тАО06-06-2006 04:26 AM
Solved! Go to Solution.
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тАО06-06-2006 05:25 AM
тАО06-06-2006 05:25 AM
SolutionIf you wish to measure this effect then reduce shmmax and leave your SGA large. Do an ipcs -ma and you will see multiple shared memory segents associated with the same Oracle instance. Do some benchmarks comparing the performance of 1 large vs multiple small segments.
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тАО06-06-2006 06:09 AM
тАО06-06-2006 06:09 AM
Re: Oracle SGA Spans Multiple Segments
Regardless, I would say that it would certainly be less overhead to let Oracle manage its shared memory segments in as few as possible. You should always try to do them in as few as possible, by making sure that shmmax is bigger than the SGA you're trying to stand up, when and where possible.
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тАО06-06-2006 06:26 AM
тАО06-06-2006 06:26 AM
Re: Oracle SGA Spans Multiple Segments
Thank you for the insight. Yes, 64-bit HP-UX 11.00 and Oracle 8i on this box.
# kmtune |grep shmmax
shmmax 1073741824
# ipcs -ma |awk '/oracle/ {print $10}'
1073741824
564658176
579985408
The first two lines are the buffer cache, and the third is the remainder of the pools.
I won't be able to reboot for some time, so I was hoping someone could provide specific before and after figures from a similar adjustment (SGA in three segments with shmmax set to 1GB to one segment with shmmax at, say, 3GB). I'm basically wondering if it's worth recompiling just for this.
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тАО06-06-2006 06:49 AM
тАО06-06-2006 06:49 AM