Oracle 11.2 on AIX 7.1 JFS2 mount options

From: Martin Klier - Performing Databases GmbH <>
Date: Wed, 21 Dec 2016 20:46:02 +0100 (CET)
Message-ID: <>

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 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 >=

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 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 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 ( 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The IBM papers on that are REALLY GOOD but are all a bit outdated: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 and AIX 7.x.

Thanks a lot in advance!

Martin Klier

Martin Klier | Performing Databases GmbH 
Managing Partner | Senior DB Consultant 
Oracle ACE | 

Received on Wed Dec 21 2016 - 20:46:02 CET

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