If the database is open, shut it down using the command SHUTDOWN ABORT.
Restore the damaged datafiles from the most recent backup files. Remember, do not restore any undamaged datafiles or online redo log files.
Start the database in mount mode by issuing the STARTUP MOUNT command.
To make sure all datafiles needing recovery are online during complete media recovery, issue the ALTER DATABASE DATAFILE 'FILENAME' ONLINE; statement. If the specified datafile is already online, Oracle just ignores this statement.
To start closed database recovery, issue the RECOVER DATABASE command for all damaged datafiles in one step, or the RECOVER DATAFILE command for an individual damaged datafile.
Unless the application of redo log files is automated, Oracle will prompt you for each required redo log file.
When recovery is finished, all datafiles are synchronized. Open the database by issuing the ALTER DATABASE OPEN; command.