Disabling concurrent I/O and direct I/O on Domino servers on AIX

Concurrent I/O (CIO) and Direct I/O (DIO) are not supported with Domino® servers. CIO is a file system feature introduced in IBM® AIX®, also known as maintenance level 01, in the Enhanced Journaling File system (JFS2). This feature improves performance for relational databases.

About this task

Because the CIO feature is not supported for use with Domino servers, do not enable this option on file systems that Domino accesses. If this option is enabled, Domino data might become corrupted, which can cause server crashes or performance issues.

Certain core file system items, such as file buffer cache, per-file lock or inode lock, and sync daemon, are managed differently by the operating system with the CIO option enabled. Domino is not coded to address these changes in behavior.

The following example shows the output with CIO disabled:

/dev/test05lv     /test05 jfs2   Oct 09 23:13 rw,log=INLINE

The following example shows the output with CIO enabled:

/dev/test03lv /test03  jfs2   Sep 19 19:25 rw,cio,log=INLINE

For more information on the CIO feature, refer to the IBM whitepaper Improving Database Performance With AIX Concurrent I/O listed in the Related information section at the end of this topic..

The CIO option is typically enabled as a flag when a file system is mounted. Use these steps to disable the mount option:


  1. Run this command for each file system mounted with CIO:
    chfs -a options=rw /FS_NAME

    Where /FS_NAME is the name of the mount point.

  2. Unmount and remount each file system, or reboot, which has the same effect when done after running the chfs commands.
  3. To verify that the change was applied, run 'mount' and verify that you do not see "cio" in the mount options column.