I also have this same set up for DBB: Full backups daily (automagically) to 
scratch tape device and a trigger set for incremental to disk at 75% full to 
avoid  log full situations.  BUT..... once my auto backup kicks off and waits 
for a tape mount (could possibly be hours), adsm is unable to accept any other 
Database commands (including an incr backup to disk)  

Catch-22 ...?