5 GB SGA on 8GB RAM HP Server 64Bit

Question

Hi all
Recently three months we installed Oracle 10g Database on HP Server (having 4 XEON Processors) with Windows 2003 (64 Bit) OS and we have 8GB RAM.
We wished to have 5500M as the SGA Target but we could not configure more that 3800M on that machine as after that it would error and the database would not get start.
error messages would be like - Out of memory
OR
???? (not recollecting)
Now we are running with only 3500M as sga_target and not utilizing the full available RAM with us. Of course we are using in addition 1500M for pga_aggregate_target without any problem. Even if we increase pga_aggregate_target to 3000M there is no problem but that is not desired to us. We wish to increase sga_target.
We are getting excellent response timings on 3500M sga_target but as human nature would be , we wish to be more greedy and use the full available RAM with us i.e 8GB out of which we can safely use 7GB for Oracle instance. While deducting 1500M for pga_aggregate_target we would like to use 5500M for sga_target.
Any help is appreciated.
Suresh Bansal

Answer 1

Excerpt from oracle docs.
Benefits of Automatic Shared Memory Management
Automatic Shared Memory Management simplifies the configuration of the SGA. Before Oracle Database 10G, buffer cache, shared pool, java pool, and large pool need to be manually specified for the database. Under sizing can lead to poor performance and out-of-memory errors (ORA-4031), while over sizing can waste memory. This feature enables you to specify a total memory amount to be used for all SGA Components (buffer cache, shared pool, java pool, and large pool). The Oracle database periodically redistributes memory between these components according to workload requirements. Before Oracle Database 10G, the user did not have exact control over the total size of the SGA since memory was allocated by Oracle for the fixed SGA, and for other internal metadata allocations over and above the total size of the user specified SGA parameters. The new SGA size parameter SGA_TARGET now includes all the memory in the SGA, including all the automatically sized components, manually sized components, and any internal allocations during startup.
Configuring Automatic Shared Memory Management
Automatic Shared Memory Management can be configured by using the SGA_TARGET initialization parameter. If you specify a non-zero value for SGA_TARGET, the following four memory pools are automatically sized:
* Database buffer cache (Default pool)
* Shared pool
* Large pool
* Java pool
If you set SGA_TARGET to 0, Automatic Shared Memory Management is disabled. The default value of SGA_TARGET is 0.
The individual parameters used before Oracle 10G releases to specify the sizes of the automatically sized components have not been made obsolete. The initialization parameters that size these pools (DB_CACHE_SIZE, SHARED_POOL_SIZE, LARGE_POOL_SIZE, and JAVA_POOL_SIZE) are now referred to as auto-tuned SGA parameters.
The following buffers are now referred to as manually sized components:
* Log buffer
* Other buffer caches (KEEP/RECYCLE, other block sizes)
* Streams pool (new in Oracle Database 10g)
* Fixed SGA and other internal allocations
Note: STATISTICS_LEVEL must be set to TYPICAL (default) or ALL to use Automatic Shared Memory Management.
Jaffar