If a database was terminated while one of its tablespaces was in
BACKUP MODE (ALTER TABLESPACE xyz BEGIN BACKUP;), it will tell you
that media recovery is required when you try to restart the database.
The DBA is then required to recover the database and apply all
archived logs to the database. However, from Oracle7.2, you can
simply take the individual datafiles out of backup mode and restart the
database.
ALTER DATABASE DATAFILE '/path/filename' END BACKUP;
One can select from V$BACKUP to see which datafiles are in backup
mode. This normally saves a significant amount of database down
time.
Thiru Vadivelu contributed the following:
From Oracle9i onwards, the following command can be used to take all
of the datafiles out of hot backup mode:
ALTER DATABASE END BACKUP;
The above commands need to be issued when the database is
mounted.