Recently I came across a small but strange problem with an AIX 5.3 system running Oracle. When we tried to perform an offline filesystem backup of the sapdata1 filesystem, we received errors stating the certain files were not able to opened. I confirmed this by using the 'file' command on some of the database files. I received the following messages:

gibsonc@hxaix35 /oracle/TC0/sapdata1/sr3_6 $ file sr3.data6

sr3.data6: 0653-902 Cannot open the specified file for reading.

I discovered that the sapdata1 filesystem had not been mounted with the CIO (Concurrent I/O) option. CIO was enabled within the Oracle database, however.

gibsonc@hxaix35 /home/gibsonc $ mount | grep sapdata

         /dev/sapdata1_TC0lv /oracle/TC0/sapdata1 jfs2   Jan 24 23:26 rw,log=/dev/loglv01

After rectifying this and mounting the filesystem again with the CIO option, the problem disappeared.

gibsonc@hxaix35 /home/gibsonc $ mount | grep sapdata

         /dev/sapdata1_TC0lv /oracle/TC0/sapdata1 jfs2   Jan 24 23:26 rw,cio,log=/dev/loglv01

gibsonc@hxaix35 /oracle/TC0/sapdata1/sr3_6 $ file sr3.data6

sr3.data6: data or International Language text

We were then able to perform our backup.

The following IBM Technote outlines why this happens.

Issues opening files in CIO or DIO mode:

http://www-01.ibm.com/support/docview.wss?rs=1209&context=SWG10&dc=DB520&q1=inode+jfs2&uid=isg3T1010931&loc=en_US&cs=UTF-8&lang=en