Re: Oracle 11.2 on AIX 7.1 JFS2 mount options

From: Stefan Koehler <>
Date: Wed, 21 Dec 2016 21:17:08 +0100 (CET)
Message-ID: <>

Hey Martin,
short answer - SAPnote #948294 is correct. Long answer on page 59/60 here:

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:
Twitter: _at_OracleSK  

> Martin Klier - Performing Databases GmbH <> 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 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 - 21:17:08 CET

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