Use Disk Caching
If Oracle cannot find the data it needs in the buffer cache or PGA, it performs a physical read. But
how many of the physical reads actually reach the disk? If you use disk caching, you may be able
to prevent 90 percent or more of the access requests for the most-needed blocks. If the database
buffer cache hit ratio is 90 percent, you are accessing the disks 10 percent of the time??”and if the
130 Oracle Database 11g DBA Handbook
disk cache prevents 90 percent of those requests from reaching the disk, your effective hit ratio is
99 percent. Oracle??™s internal statistics do not reflect this improvement; you will need to work with
your disk administrators to configure and monitor the disk cache.
Use a Larger Database Block Size
There is only one reason not to use the largest block size available in your environment for a new
database: if you cannot support a greater number of users performing updates and inserts against
a single block. Other than that, increasing the database block size should improve the performance
of almost everything in your application. Larger database block sizes help keep indexes from
splitting levels and help keep more data in memory longer. If you are experiencing buffer busy
waits during inserts, increase the settings for the freelists parameter setting at the object level (if
you are using Automatic Segment Space Management, the freelists parameter does not apply).
Design to Throughput, Not Disk Space
Take an application that is running on eight 9GB disks and move it to a single 72GB disk.
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