RMAN on AIX !!

I am setting up RMAN on AIX. Currently the AIX uses it's proprietary backup to tapes just by using the tapeutil command, no third party tool for backing up to tapes.

So do I need to re-link the media manager library to oracle executable ??

The AIX command to write to tapes is tapeutil -f /dev/rmt1 unmount 41.
then backup....

DO I need to do in RMAN the following:

allocate channel xxx type disk;
and then
format '/dev/rmt1' etc or do I need to use the sbt_tape command which gives an error message.

If your media manager supports RMAN, then yes, you have to replace the current libobk and relink oracle to use device SBT_TAPE. However, if you are using an OS utility, it probably doesn't support RMAN.

Your use of type DISK is interesting. I think I read somewhere that RMAN doesn't like this because it does some funky I/O at the begining of the job. I don't remember the specifics, but it would be interesting to try...

Also, Oracle has a run-time version of Legato that you can use with RMAN. I've used it before with a simple tape device and it works OK.