Hi I am receiving the following backup error when using backup -0uf /dev/rmt0.1 for the file system

backup: Backing up /dev/rfslv00 (/u04) to /dev/rmt0.1.
backup: 0511-251 The file system is still mounted; data may not be consistent.
Use the umount command to unmount the filesystem; then do the backup.
backup: Mapping regular files. This is Pass 1.
backup: Mapping directories. This is Pass 2.
backup: There are an estimated 86378845 1k blocks.
backup: Backing up directories. This is Pass 3.
An error occurred when reading data from the device.
backup: 0511-203 Internal error; exit status 1 is not recognized.
backup: 0511-230 Pipe communication is ended. Try the backup again later.

there are a number of filesystems succesfully backed up before we get to this filesystem. When the error occurs the backup simply hangs until we kill it
We have been backing up this filesystem for several years with no problems. We have changed tapes and used a tape head cleaner but with no effect, the error still occurs. The 0511-251 message can be ignored as this always happens if you are backing up mounted filesystem ( and all the previous ones backup ok with the same message )
The problem appears to be the 0511-203 error

Any ideas ?

There are a few things that may be the problem here

1. Depending on your oslevel and jfs vertion there use to be a but that was fixed with apar IY71476. This was fixed in aix5300-03

2. The more likely problem is a corupt file system and you may have to check the filesystems for erros using fsck

3. Last problem is tape problem but as you have alredy used this for backup