Tuning Oracle Database - SGA Memory

Question

Good morning Gurus,
  I have this environment in my company:
  SAP ECC 6
  Oracle 10g
  Aix 6.1
Our hardware resources:
  Memory: 16GB Ram
  Processor: 4 x 3.2Ghz
  IBM Blade JS12
  Recently, we migrated SAP 4.6C (Solaris) to SAP ECC (Aix). In this new version, a lot of users feel that the performance had decreased.
  I checked SGA Memory in Oracle, and i noticed that this configuration didn't used all hardware resources.
  This parameters was like these:
  sga_max_size=712M
  pga_aggregate_target=292M
  db_cache_size=292M
  processes=80
  sessions=96
  I changed for:
  pga_aggregate_target = 4096M
  sga_max_size = 4096M
  sga_target = 4096M
  db_cache_size = 600M
   I noticed, after this change the performance was perfect. We reduced the time db execution in 60%, but now it isn't occur.
   We changed this parameters on July 4nd, now the performance decrease in 30%.
   My question is, after this change, do we need to adjust the parameters in profile?
Thanks very much
Denis
Brazil

Answer 1

Gerd Kirchner wrote:
> Note 617416 is pretty old (2006), you should follow note 830576 for 10g and there is no sga_max_size mentioned.
Yes it is old, because there are no significant changes on automatic memory management between 9i and 10g (11g is another history), so it is "valid"
sga_max_size is not mentioned in note 830576 because the memory parameters depend on the available memory. look at the recommendations for the other "memory" parameters:
DB_CACHE_SIZE                    Size depends on the available  memory (Notes 789011, 617416)
LOG_BUFFER                       1048576
PGA_AGGREGATE_TARGET             OLTP: 20 % of available memory
                                 OLAP: 40 % of available memory
SHARED_POOL_SIZE                 400 MB or greater, refer to Note 690241
As you see, there is only one "hard coded" recommendation and one minimum recommendation.
It is not possible to give a recommendation for sga_max_size.
If you do not set it, Oracle automatically calculates it.
If it is set to small, Oracle will adjust it.
What it is important is to set up the DB_CACHE_SIZE and SHARED_POOL_SIZE, they will be the MINUMUM sizes if AMM is
used