To restore a physical backup of a datafile or control file is to reconstruct it and make it available to the Oracle database server. To recover a restored datafile is to update it by applying archived redo logs and online redo logs, that is, records of changes made to the database after the backup was taken. If you use RMAN, then you can also recover restored datafiles with incremental backups, which are backups of a datafile that contain only blocks that changed after a previous incremental backup.
After the necessary files are restored, media recovery must be initiated by the user. Media recovery can use both archived redo logs and online redo logs to recover the datafiles. If you use SQL*Plus, then you can run the RECOVER command to perform recovery. If you use RMAN, then you run the RMAN RECOVER command to perform recovery.
To recover the standby database after the loss of one or more data files, you must restore the lost files to the standby database from the backup using the RMAN RESTORE DATAFILE command. If all the archived redo log files required for recovery of damaged files are accessible on disk by the standby database, restart Redo Apply.
If the archived redo log files required for recovery are not accessible on disk, use RMAN to recover the restored data files to an SCN/log sequence greater than the last log applied to the standby database, and then restart Redo Apply to continue the application of redo data, as follows:
1. Stop Redo Apply.
2. Determine the value of the UNTIL_SCN column, by issuing the following query:
SQL> SELECT MAX(NEXT_CHANGE#)+1 UNTIL_SCN FROM V$LOG_HISTORY LH, V$DATABASE DB WHERE LH.RESETLOGS_CHANGE#=DB.RESETLOGS_CHANGE# AND LH.RESETLOGS_TIME = DB.RESETLOGS_TIME;
3. Issue the following RMAN commands to restore and recover data files on the standby database. You must be connected to both the standby and recovery catalog databases (use the TARGET keyword to connect to standby instance):
RESTORE DATAFILE <n,m,…>;
RECOVER DATABASE UNTIL SCN 967786;
To restore a tablespace, use the RMAN ‘RESTORE TABLESPACE tbs_name1, tbs_name2, …’ command.
4. Restart Redo Apply.