Hey Martin,
short answer - SAPnote #948294 is correct. Long answer on page 59/60 here:
http://tinyurl.com/o6uj6mf
However please make sure that the JFS2 block size (for redo file systems) is
aligned with the redo log block size in case of direct or concurrent I/O
- otherwise you gonna run into demoted I/Os and Oracle needs two I/Os for one
(first concurrent I/O fails silently and the next falls back to normal
I/O). You can trace this with AIX kernel tracing events 59B,59C.
Best Regards
Stefan Koehler
Freelance Oracle performance consultant and researcher
Homepage: http://www.soocs.de
Twitter: @OracleSK
Martin Klier - Performing Databases GmbH <martin.klier@xxxxxxxxxxxxxxxxx> hat--
am 21. Dezember 2016 um 20:46 geschrieben:
Hi listers,
I am calling out for Oracle-on-AIX knowledge/experience bearers, and have a
question whether setting the "cio" mount option for datafiles, redo
logs and control files for DB version 11.2.0.4 on AIX 7.1 with JFS2 or not.
We are using filesystemio_options=setall for this customer setup.
The documentation situation is a bit confusing:
+ MOS Recommendations For Using CIO/DIO For Filesystems Containing Oracle
Files On AIX (Doc ID 960055.1) says:
"You need to set the CIO flag explicitly if you are not using
filesystemio_options=setall (or not using JFS2).
The CIO/DIO recommendations for filesystems containing Oracle Files are:
Data Base Files (DBF)
Use CIO or no mount options for extremely sequential I/O"
+ SAP OSS Note 948294 - AIX JFS2: mount options to use with Oracle 10g / 11g
says:
"AIX 6.1 with Oracle >= 11.2.0.2:
AIX 6.1 introduced a new open flag O_CIOR which is same as O_CIO, but this
allows subsequent open calls without CIO. The advantage of this
enhancement is that other applications like cp, dd, cpio, dbv can access
database files in read only mode without having to open them with CIO.
Starting with Oracle 11.2.0.2 when AIX 6.1 is detected, Oracle will
use O_CIOR option to open a file on JFS2.
Therefore you should no longer mount the filesystems with mount option -o cio
Please remove the mount option "-o cio" if you are running Oracle 11.2.0.2
on AIX 6.1 to avoid the following error messages:
cp: A system call received a parameter that is not valid.
0653-902 Cannot open the specified file for reading.
DBV-00100: Specified FILE not accessible
errno(22) A system call received a parameter that is not valid."
+ The Oracle "Database Administrator's Reference" says:
"Note: For Oracle Database 11g Release 2 (11.2.0.2) and later, on AIX 6.1
systems, Oracle recommends that you do not use the cio option on a JFS2
file system."
The IBM papers on that are REALLY GOOD but are all a bit outdated:
"AIX Performance: Configuration & Tuning for Oracle & Oracle RAC (Vijay
Adik)"
"Oracle DB and AIX Best Pratices for Performance & tuning (Ronan Bourlier &
Loïc Fura)"
Simple question:
I have massively concurrent IO on datafiles (usual read/write activity) and
redo logs (streams capture) with many (so far unavoidable) "db file
sequential read" and "log file sync" waits.
Should I activate JFS2 mount option -cio for my data files and redo log file
systems?
Maybe that's more a starting point for a discussion rather than an end. I'd
love to understand better how the mechanics behind changed in 11.2.0.4
and AIX 7.x.
Thanks a lot in advance!
Martin Klier
--
Martin Klier | Performing Databases GmbH
Managing Partner | Senior DB Consultant
Oracle ACE
martin.klier@xxxxxxxxxxxxxxxxx | http://www.performing-databases.com
