RMAN Retore & Recover

Use the RMAN RESTORE command to restore the following types of files from copies on disk or backups on other media:

· Database (all datafiles)
· Tablespaces
· Control files
· Archived redo logs
· Server parameter files

Automates the procedure for restoring files. When you issue a RESTORE command, RMAN restore the correct backups and copies to either:

· The default location, overwriting the old files with the same name
· A new location, which you can specify with the SET NEWNAME command

RMAN Backup Clause Syntax

   RECOVER [DEVICE TYPE deviceSpecifier [, deviceSpecifier]...]
               recoverObject [recoverOptionList];

Steps for media recovery Using RMAN

Step 01:

Mount or open the database. Mount the database when performing whole database recovery, or open the database when performing online tablespace recovery.

STARTUP FORCE MOUNT;

Step 02:

To perform incomplete recovery, use the SET UNTIL command to specify the time, SCN, or log sequence number at which recovery terminates. Alternatively, specify the UNTIL clause on the RESTORE and RECOVER commands.

Step 03:

Restore the necessary files with the RESTORE command.

Step 04:

Recover the datafiles with the RECOVER command.

Step 05:

Place the database in its normal state. For example, open it or bring recovered tablespaces online.

Restore and recover the whole database

RMAN> STARTUP FORCE MOUNT;
RMAN> RESTORE DATABASE;
RMAN> RECOVER DATABASE;
RMAN> ALTER DATABASE OPEN;

Script Code:
STARTUP NOMOUNT;
RUN
{
   ALLOCATE CHANNEL c1 DEVICE TYPE sbt;
   RESTORE DATABASE;
   ALTER DATABASE MOUNT;   
   RECOVER DATABASE;
}

Restore and recover a tablespace

RMAN> SQL 'ALTER TABLESPACE users OFFLINE';
RMAN> RESTORE TABLESPACE users;
RMAN> RECOVER TABLESPACE users;
RMAN> SQL 'ALTER TABLESPACE users ONLINE';

Restore and recover a datafile

RMAN> SQL 'ALTER DATABASE DATAFILE 32 OFFLINE';
RMAN> RESTORE DATAFILE 32;
RMAN> RECOVER DATAFILE 32;
RMAN> SQL 'ALTER DATABASE DATAFILE 32 ONLINE';

Restore and recover the Control file from Backup

Restore the control file, (to all locations specified in the parameter file) then restore the database, using that control file:

STARTUP NOMOUNT;
RUN
{
   ALLOCATE CHANNEL c1 DEVICE TYPE sbt;
   RESTORE CONTROLFILE;
   ALTER DATABASE MOUNT;
   RECOVER DATABASE;
}

Create a new control file

If all control file copies are lost, you can create a new control file using the NORESETLOGS option and open the database after doing media recovery. An existing standby database instance can generate the script to create a new control file by using the following statement

SQL> ALTER DATABASE BACKUP CONTROLFILE TO TRACE NORESETLOGS;

Recovery from the Loss of an Online Redo Log File

To add a new member to a redo log group, issue the following statement:

SQL> ALTER DATABASE ADD LOGFILE MEMBER 'log_file_name' REUSE TO GROUP n

Disaster Recovery

In a disaster situation where all files are lost you can only recover to the last SCN in the archived redo logs. Beyond this point the recovery would have to make reference to the online redo logs which are not present. Disaster recovery is therefore a type of incomplete recovery.

Step 01: Connect to RMAN

$rman catalog=rman/rman@orcl target=sys/oracle@orcl

Step 02: Recover the control file if needed.

RMAN> startup nomount;
RMAN> restore controlfile;
RMAN> alter database mount;

Step 03: Collect the last SCN using SQL*Plus as SYS

SQL> SELECT archivelog_change#-1 FROM v$database;

ARCHIVELOG_CHANGE#-1
--------------------
             1203813

Step 04: Restore and Recover database using RMAN.

 
RMAN> run {
        set until scn 1203813;
        restore database;
        recover database;
        alter database open resetlogs;
        }

Restore Validation

Restore Validation confirms that a restore could be run, by confirming that all database files exist and are free of physical and logical corruption, this does not generate any output.

RMAN> RESTORE DATABASE VALIDATE;