RE: Question about SGA memory allocation and sizing
- From: "Walker, Jed S" <Jed_Walker@xxxxxxxxxxxxxxxxx>
- To: "pjhoraclel@xxxxxxxxx" <pjhoraclel@xxxxxxxxx>, oracle-l <oracle-l@xxxxxxxxxxxxx>
- Date: Wed, 5 Sep 2012 16:50:59 +0000
The "fixed" portion is just oracle tracking itself. The variable size is the
various pools. Oracle has put the other 85GB there to manage your shared,
large, java, etc. pools. Tom Kyte describes it here
http://asktom.oracle.com/pls/asktom/f?p=100:11:26779324172700::::P11_QUESTION_ID:365088445659
I wonder if you really need the amount of memory you have allocated. You might
want to look at some of the "advice" views - v$sga_target_advice,
v$memory_target_advice, etc and check the spfile/init file __ parameters for
what oracle is using. The more memory allocated the more work for the OS and
Oracle to manage it, which segues to
If you do use that large of an SGA you might want to consider using Huge Pages.
When I implemented on a large memory system (memory target 64GB) I found a
performance improvement. I have steps for that here
http://tinky2jed.wordpress.com/technical-stuff/oracle-stuff/configuring-hugepages-for-oracle-database/
I hope that helps
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On
Behalf Of Peter Hitchman
Sent: Wednesday, September 05, 2012 10:16 AM
To: oracle-l
Subject: Question about SGA memory allocation and sizing
Hi,
This is a 11.2 database with Automatic Memory Management with a memory_target
and memory_max_target of 101GB.
Looking at v$sga I see this:
select name, value/1024/1024/1024
from v$sga
/
NAME VALUE/1024/1024/1024
-------------------- --------------------
Fixed Size 0
Variable Size 85
Database Buffers 15
Redo Buffers 0
Then looking at v$sga_resize_ops:
select component
, AVG(FINAL_SIZE)/1024/1024/1024 "AVG FINAL",
MEDIAN(FINAL_SIZE)/1024/1024/1024 "MEDIAN FINAL",
MAX(FINAL_SIZE)/1024/1024/1024 "MAX FINAL"
from v$sga_resize_ops
group by component
/
COMPONENT AVG FINAL MEDIAN FINAL MAX
FINAL
------------------------- ------------------- -------------------
-------------------
ASM Buffer Cache 0 0
0
DEFAULT 16K buffer cache 0 0
0
DEFAULT 2K buffer cache 0 0
0
DEFAULT 32K buffer cache 0 0
0
DEFAULT 4K buffer cache 0 0
0
DEFAULT 8K buffer cache 0 0
0
DEFAULT buffer cache 21 21
26
KEEP buffer cache 0 0
0
RECYCLE buffer cache 0 0
0
java pool 0 0
0
large pool 0 0
0
*shared pool 14 14
20*
streams pool 1 1
1
Given that the shared pool has a max value of 20GB and the other pools are
effectively 0, that the rest of the space for the variable part of the SGA is
free?
If so, why did Oracle decide to allocate 85GB?
Thanks
Pete
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