When a file system has heavy I/O, the umount command can take several minutes to respond. However, the umount command temporarily deletes the mount point from mount command output while processing. Per IBM, this is the expected and supported behavior on AIX. The umount command's processing later puts the mount point back if the mount point is found busy. Meanwhile, the default OfflineTimeout value of the Mount agent can get exceeded, which in turn invokes the Clean agent function. The Clean function can find the mount point's entry absent from the mount command output and exit with success.

The unmounting, however, may not have happened yet. If unmounting did not occur, offlining resources below the Mount resource (for example the LVMVG or DiskGroup resources) can fail.

The Mount resource's Offline agent function then proceeds to unmount the mount point. After several attempts, the Clean scripts that clean the resources below the Mount resource succeed and the group goes offline.

See the Veritas Cluster Server Administrator's Guide for more information about the OfflineTimeout attribute.