IBM Power7 Optimization And Tuning Manual page 207

Buffered file I/O on JFS2:
– The default is filesystemio_options=ASYNC.
– In this case, all data spaces, redo log file systems, and control file systems are using
the kernel buffers rather than writing directly to disk.
– In this case, it does not matter whether redo log file systems and control file systems
are 512 byte or 4 KB block size file systems.
– The best performance for Oracle on AIX or Power Systems is, however, usually
achieved by using CIO (though there are exceptions).
Concurrent I/O (CIO) on JFS2:
– Set the Oracle parameter filesystemio_options=SETALL or mount the file systems
(other than dump devices) with the CIO option. It is not necessary to use both SETALL
and mount file systems with the CIO option, although no harm is done either way.
Metalink note: 272520.1 indicates that mounting with CIO is needed at the time of the
writing of this guide.
– If you use CIO with SETALL, CIO mount, or both, you
for redo logs and control files (or a single file system for both), with an agblksize of 512
rather than the default 4 KB.
– The ioo parameter fs_fastpath accelerates CIO. It is enabled by default in AIX V6.1
and AIX V7.1.
IBM mount advice for database files:
– Data files: Use the CIO parameter filesystemio_options=SETALL, with a default of
agblksize (4 KB). Use mount with no options.
– Redo logs: Create the logs with agblksize of 512 and mount with no options. With
SETALL, use direct I/O for Redo logs.
– Control files: Create the files with agblksize of 512 and mount with no options. With
SETALL, use direct I/O for Redo logs.
– Archive logs: Run mount -o rbrw. Do not use CIO; use the jfs2 rbrw option.
– Dumps: Run mount –o rbrw.
– The mount option noatime, suggested for Oracle 10g, is no longer required.
IOO tunables j2_nBufferPerPagerDevice and j2_dynamicBufferPreallocation:
– Do not change these tunables unless there is a high delta in vmstat –v external pager
file system I/Os that are blocked with no fsbuf. If this value is high, first increase
j2_dynamicBufferPreallocation from 16 (16 KB slabs) to 32 and monitor the system.
If increasing this tunable does not help, then consider raising the value of
j2nBufferPerPagerDevice, which is the starting value for dynamic buffer allocation.
– For information about these parameters, see the help pages available at
http://pic.dhe.ibm.com/infocenter/aix/v7r1/topic/com.ibm.aix.cmds/doc/aixcmd
s3/ioo.htm. Do not change AIX V6.1 or AIX V7.1 restricted tunables unless directed to
do so by IBM AIX support. In AIX V6.1, j2_nBufferPerPagerDevice is a restricted
tunable, and j2_dynamicBufferPreallocation is not.
ASM considerations for stand-alone Oracle 11gR2:
– For identifying, renaming, and securing ASM raw devices, see Managing Raw Disks in
AIX to use with Oracle Automatic Storage Management (ASM) in Table C-1 on
page 186.
– ASM uses asynchronous I/O by default, so filesystemio_options=ASYNC (the default)
is appropriate.
Appendix C. POWER7 optimization and tuning with third-party applications
must
create separate file systems
191