We had significant problems with sga_target, enough that we finally
turned it off. Apparently, in 10.2.0.1 there are some issues with the
algorithm that allocates/deallocates memory which can cause degradation.
Our Support Analyst(s) referenced the following bugs:
4466399/4472338 (dup) (SR 5386579.993): SYSTEM WIDE HANG ON MMON WAITING
FOR 'SGA ALLOCATION FORCING COMPONENT GROWTH':
4507532 (SR 5256243.992): SGA_TARGET DOESN'T WORK AS EXPECTED
Not sure if this is relevant for your situation, but wanted to offer it
up just in case.
Sent: Friday, June 16, 2006 9:31 AM
Subject: Reducing sga_target in 10gR2 without getting ORA-00827
To attempt to mitigate ORA-04030
crashes we've been experiencing, Oracle
has suggested lowering sga_target. Unfortunately, the log/trace files
have provided no clues at all as to what is causing this crash every 3-5
weeks. The server has 4GB of physical RAM, but is not using the /3GB
switch so Oracle can only access 2GB. Currently sga_target is set at
1.2GB. The server runs only this 1 instance of Oracle so Windows has
plenty of mem.
select * from v$sga_dynamic_free_memory gives 0 because
sga_target=sga_max_size so Oracle has no memory to grow if needed. It
shouldn't need to since 1.2GB should be way more mem than it needs for
Based on note 295626.1 I don't think I can reduce sga_target appreciably
without getting ORA-00827
(could not shrink sga_target to specified
value). Currently the sum of the min sizes
(select component, current_size/1024/1024 "CURRENT_SIZE",
is 1188 and sga_target is 1200.
Is there any way I can reduce sga_target to 1000 dynamically? Will I
just have to keep doing it in small steps of 12 for example?
Topshot Systems LLC