The larger
the sort area size is, the less likely you are to need to use the temporary tablespace for sort
segments. The higher the multiblock read count is, the more blocks you may be able to read
during a single physical read (as limited by the operating system). Use the alter session command
to increase these values for your session.
Tuning Data Access
Even if your tables are properly configured and indexed, your performance may suffer if there
are wait events caused by file accesses. In the following sections, you will see recommendations
related to file and tablespace configuration.
In general, you should avoid placing Oracle files on distributed-parity RAID systems such as
RAID 5. The overhead generated during writes to such file systems generally presents a performance
bottleneck as the system use increases, particularly for sequentially written files such as the online
redo log files. Favor the use of RAID 0+1 to support both the mirroring and striping of data without
introducing these performance bottlenecks.
Locally Managed Tablespaces
You can use locally managed tablespaces to handle extent management within the tablespaces.
Locally managed tablespaces manage their own space by maintaining a bitmap in each datafile of
the free and used blocks or sets of blocks in the datafile. Each time an extent is allocated or freed
for reuse, the database updates the bitmap to show the new status.
258 Oracle Database 11g DBA Handbook
NOTE
As of Oracle Database 10g, all tablespaces in a default installation are
locally managed; bigfile tablespaces must be locally managed.
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