Netbackup 4.5, MP5, Oracle RMAN extension...

Oracle 8.17

What begins as a three hour duration backup for the
database slowly increases in duration, 10-15 minutes
a day, until we're pushing seven hours.  No appreciable
increase in the amount of data being backed up, although
the size of the backup is substantial.

Bouncing the database server procs seems to reset us back
to "normal" duration.

Any ideas?

Thanks.