Overview of RMAN

RMAN (Recovery Manager) performs physical backups and supports point-in-time recovery. It operates in two database modes:

• Archivelog mode: Allows both offfline (cold) and online (hot) backups.
• Noarchivelog mode: Only offline backups are permitted.

Using RMAN

Connect to the target database from the server:

rman target /
# or with a recovery catalog
rman target / catalog rman_user/password@catalog_db

From a remote client:

rman target sys/password@host:port/service_name

The connecting user must have SYSDBA privileges.

Check archiving status:

SELECT log_mode FROM v$database;
-- Enable archivelog mode
SHUTDOWN IMMEDIATE;
STARTUP MOUNT;
ALTER DATABASE ARCHIVELOG;
ALTER DATABASE OPEN;

Configure archive destination and format:

ALTER SYSTEM SET log_archive_dest_1 = 'LOCATION=/arch' SCOPE=SPFILE;
ALTER SYSTEM SET log_archive_format = 'arc_%t_%s_%r.arc' SCOPE=SPFILE;

Backup Strategies by Mode

Consistent backups occur when the database is cleanly shut down (SHUTDOWN IMMEDIATE, etc.). Inconsistent backups happen while the database is open or after a abort.

In noarchivelog mode, perform a cold backup:

SHUTDOWN IMMEDIATE;
STARTUP MOUNT;
ALTER DATABASE NOARCHIVELOG;
-- Then in RMAN:
BACKUP DATABASE FORMAT '/backup/db_%U';

In archivelog mode, online backups are possible:

BACKUP DATABASE PLUS ARCHIVELOG;

Extend control file record retention:

ALTER SYSTEM SET control_file_record_keep_time = 30;

Listing and Reporting Backups

Use LIST to inspect backups:

LIST BACKUP OF DATABASE;
LIST BACKUPSET TAG 'FULL_BACKUP';
LIST COPY OF DATAFILE 1;
LIST ARCHIVELOG ALL;

Use REPORT for analysis:

REPORT SCHEMA;
REPORT NEED BACKUP DAYS 3;
REPORT UNRECOVERABLE;
REPORT OBSOLETE;

To prevant unrecoverable operations, enable force logging:

ALTER DATABASE FORCE LOGGING;

Hot vs Cold Backups

• Hot backup: Database is open; requires archivelog mode.
• Cold backup: Database is shut down; works in any mode.

Manual cold backup involves copying all critical files: datafiles, control files, SPFILE, redo logs, and tempfiles—after cleanly shutting down the instance.

RMAN cold backup:

STARTUP MOUNT;
BACKUP DATABASE;

A backup set is a logical container; it consists of one or more backup pieces (physical files).

Crosscheck and Manual Cataloging

Verify backup existence:

CROSSCHECK BACKUP;
CROSSCHECK ARCHIVELOG ALL;

Statuses: A (available), X (expired). Clean up metadata:

DELETE EXPIRED BACKUPSET;
DELETE NOPROMPT OBSOLETE;

Manually register moved backups:

CATALOG BACKUPPIECE '/new_loc/backup_01.bkp';
CATALOG START WITH '/moved_backups/';

Register archived logs in SQL*Plus:

ALTER DATABASE REGISTER PHYSICAL LOGFILE '/arch/arc_1_123.arc';

Validating Database Integrity

Check for physical and logical corruption:

VALIDATE DATABASE;
VALIDATE TABLESPACE USERS;
VALIDATE DATAFILE 1 BLOCK 100;
VALIDATE CHECK LOGICAL DATABASE;

Alternatively, simulate backup validation without writing output:

BACKUP VALIDATE DATABASE;
BACKUP VALIDATE CHECK LOGICAL ARCHIVELOG ALL;

Use the dbv utility externally:

dbv file=system01.dbf

Block corruption types:

• Physical: Invalid checksum, zero-filled blocks, header/footer mismatch.
• Logical: Inconsistent row or index structures.

By default, RMAN detects only physical corruption; add CHECK LOGICAL to include logical checks.