Ok..you traditional HOT backup (not RMAN backup) failed or you have killed the HOT backup. Then you have check if any of the files are still active in V$backup and then do a "alter tablespace end backup" for each and every tablespace. In 10g you don't have to do that. You can do a "alter database begin backup" and "alter database end backup". These commands will either put/take the tablespaces in/out of HOT backup mode. Not sure if this is goin' to help a lot of people, 'cos now most of the people use RMAN. In case you are using traditional HOT backups ( I prefer using RMAN backups), then this might be of help to you.
Just another new feature in 10g.
Hope this helps.
-- Vish.
