RMAN backups not using next available volume: uses next unlabeled volume

Question

Greetings.
I've noticed that sometimes (haven't zeroed in on when yet) when RMAN backs up using OSB, the first tape in the library, an RMAN volume, is grabbed and backed up to.
There are about 10 other RMAN-labeled volumes right below that first one. But RMAN will take an unlabeled volume further down in the library, label it as an RMAN volume, and proceed to back up to it.
This is happening often enough where my library is filling up with partially used RMAN volumes.
Three jobs (that I can see so far) are cron jobs calling an RMAN script. I'm looking for the other jobs which, I think, are run via OEM.
Any thoughts?
-Jeff

Answer 1

Our daily backup is doing the same thing. That is, it's not backing up to tapes I assume it'll use. This is in the transcript:
2010/06/08.22:00:17 (mmr) volset containing oid 21601 (vid PASDLY-000665, tag 000020L3, create_time 1275530931, mediainfo 0) is closed
2010/06/08.22:00:17 (amh) 18 oid 21601 doesn't meet mount requirements - volume set is closed to further update (OB device mgr)
2010/06/08.22:00:17 (mmr) volset containing oid 21607 (vid PASDLY-000667, tag 000114L3, create_time 1275617100, mediainfo 0) is closed
2010/06/08.22:00:17 (amh) 19 oid 21607 doesn't meet mount requirements - volume set is closed to further update (OB device mgr)
2010/06/08.22:00:17 (mmr) volset containing oid 21597 (vid PASDLY-000664, tag 000004L3, create_time 1275444068, mediainfo 0) is closed
2010/06/08.22:00:17 (amh) 20 oid 21597 doesn't meet mount requirements - volume set is closed to further update (OB device mgr)Where do I find how the mount requirements are configured?
-Jeff