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Home -> Community -> Mailing Lists -> Oracle-L -> RE: 9i - Dynamic SGA - SGA_MAX_SIZE
Venu,
this does help and this is what the guys on metalink said.
What I do not understand - what a waste.
If I have to grab 100M initially on the OS side I may aswell use it.
In my metalink tar I quoted many references in the documentation:
E.G.
In the Database Administration guide:
Chapter 2: 'The size of the SGA is dynamic, and can grow or shrink by
dynamically altering these parameters.'
Now I would say grabing the SGA_MAX_SIZE for the entire uptime of the
database is not what I would call dynamic.
I can't see any growing or shrinking in SGA size.
Stephen Hodgkinson
Oracle DBA
TotalFina Elf Gas & Power Ltd
Phone: 01737 27 5564
stephen.hodgkinson_at_eaguk.com
"Venu Gopal"
<venu.andem_at_wi To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
pro.com> cc:
Sent by: Subject: RE: 9i - Dynamic SGA - SGA_MAX_SIZE
ml-errors_at_fatc
ity.com
01/08/03 12:14
Please respond
to ORACLE-L
Stephen,
That's the way it's meant to work.
This is how Oracle guarantees that you can grow upto the value of
SGA_MAX_SIZE. Look at the case below:
DAY 1: you have your sga_max set to 100m but you are currently using
only 50m of it.
DAY 2: you want to use all 100m and you try to increase the sga size,
but some other app has used rest of the physical memory and there is no
sufficient memory available, at this stage oracle has to error out
saying 'insufficient memory', but in reality it does not!!
In reality: On DAY 1, Oracle tries to occupy all 100m in the memory so that it doesn't have any issues in future... this way you have 100m reserved for oracle, use it whenever you want to use it.
Hope this helps you...
~Venu
-----Original Message-----
Stephen.HODGKINSON_at_eaguk.com
Sent: Friday, August 01, 2003 3:24 PM
To: Multiple recipients of list ORACLE-L
Hi,
does anybody have any experience with setting the SGA_MAX_SIZE in 9i.
I assumed the purpose of this parameter was that SGA would grow as requested to that limit.
Example:
You could configure your SGA to be 80M
Set the SGA_MAX_SIZE to be 250M.
I would have expected oracle to acquire 80M of memory from the UNIX machine.
In fact using ipcs you can see that oracle will always acquire the
value
of SGA_MAX_SIZE.
It acquires the extra space in the Variable Size of the SGA
Sga_max_size=75m.
Show sga:
Total System Global Area 77041728 bytes
Fixed Size 733248 bytes
Variable Size 41943040 bytes
Database Buffers 33554432 bytes
Redo Buffers 811008 bytes
sga_max_size=110M and keep everything else the same.
show sga:
Total System Global Area 114790680 bytes
Fixed Size 733464 bytes
Variable Size 79691776 bytes
Database Buffers 33554432 bytes
Redo Buffers 811008 bytes
Database mounted.
Database opened.
I have raised a lengthy call on Metalink and the consultants are
convinced
this is normal behaviour and what you would expect.
Do people agree with the metalink consultants?
Maybe my expectations were to high but I thought a dynamic sga would
mean I
could change the amount of memory acquired by the UNIX box.
All opinions welcome. I am on tru64 platform - 9.2.0.3.0
Thanks, Stephen
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