| What should be recommended percentage of memory to be used for oracle [message #632237] |
Wed, 28 January 2015 00:49  |
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juniordbanewbie
Messages: 250
Registered: April 2014
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Senior Member |
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Hi all,
from http://docs.oracle.com/cd/E11882_01/server.112/e41573/memory.htm#i47856
Quote:
For OLTP: PGA_AGGREGATE_TARGET = (total_mem * 80%) * 20%
For DSS: PGA_AGGREGATE_TARGET = (total_mem * 80%) * 50%
where total_mem is the total amount of physical memory available on the system.
80% percent of physical memory is to be used for oracle database instances.
from 567506.1 Maximum SHMMAX values for Linux x86 and x86-64
Quote:
Oracle Global Customer Support officially recommends a " maximum" for SHMMAX of "1/2 of physical RAM".
from 1527109.1 Relationship Between SGA_TARGET and SHMMAX
Quote:
Ideally, we would like SGA_TARGET to fit in one shared memory segment at startup by having SGA_TARGET < SHMMAX
okay let me figure out this if I'm using automatic shared memory management model.
Let's say we have a physical memory of 16 GB, => shmax=>2^4*2^30, i.e 17179869184
my SGA_target will be then be 8G. =>I get this value based on 567506.1 Maximum SHMMAX values for Linux x86 and x86-64
If I based on http://docs.oracle.com/cd/E11882_01/server.112/e41573/memory.htm#i47856
For OLTP: PGA_AGGREGATE_TARGET = (total_mem * 80%) * 80%
now SGA_target should be = (total mem*80%)*80
=10.24G
For DSS: PGA_AGGREGATE_TARGET = (total_mem * 80%) * 50%
=6.4 G
Based on method one, I calculate SGA to be 8 G while that of method 2, I get 10.24 G or 6.4, would like to know how much percent of memory should we allocate to oracle database instances?
also would like to know why the differences if my method of calculating is sga_target is correct.
many thanks!
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| Re: What should be recommended percentage of memory to be used for oracle [message #632326 is a reply to message #632323] |
Thu, 29 January 2015 01:31  |
John Watson
Messages: 8927
Registered: January 2010
Location: Global Village
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Senior Member |
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That's exactly it. Before I worked for Oracle, I used to think that Oracle Support knew it all. Well, they don't - they are just ordinary blokes like you and me. Heck, they were[/italic] me. Perhaps they have done one or two more courses than the average user (Uncle Oracle is good about internal training) but that may be all. They do not have access to any more information than we do. Yes, some MOS articles are hidden from the public, but not that many. We all see the same database, use the same search tools. Furthermore, unless things have changed, the support structure is very flat: any TAR might be picked up by someone with twenty years experience, or by some kid hired just a couple of months ago.
I should qualify all of the above by saying that things may well have changed - it is a long time since I worked for Larry.
[Updated on: Thu, 29 January 2015 01:31] Report message to a moderator |
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