DBA SGA+PGA Memory Configuration
Categories: DBA, Enginatics
A frequent configuration problem is not making full use of the available hardware resources, especially the physical RAM of the database server.more less
This report shows the servers SGA, PGA and CPU configuration in comparison to the available hardware.
For maximum performance, configure the SGA+PGA to use the full available memory of your server minus a few gig for OS level caching, e.g. for writi... ng and reading of PLSQL output files on the DB node and for process memory (an estimated 4MB per process, see below).
Oracle's performance tuning guide:
Oracle's exadata best practices whitepaper:
SUM of databases (SGA_TARGET + PGA_AGGREGATE_TARGET) + 4 MB * (Maximum PROCESSES) < Physical Memory per Database Node
Tom Kyte's recommendation:
"... if you want it all automatic, give ALL FREE MEMORY on your machine to the SGA and be done with it. No more monitoring, no more thinking about how it could be, should be, would be used.
Set the PGA aggregate target and the SGA target to be a tad less than physical memory on the machine and you are done."
The report also shows the status of system statistics.
select * from sys.aux_stats$
If CPUSPEEDNW still shows the default of 4096, it either means that the stats have never been gathered or it could also mean that your storage is too fast to gather them with the standard NOWORKLOAD method and you should set reasonable values manually then.
There is also an Exadata mode, considering the faster storage correctly and updating the MBRC too
exec dbms_stats.gather_system_stats(`EXADATA'); more