Backup, Recovery and Administration

Database administration encompasses backup and recovery, space management, performance monitoring, patching, and day-to-day operations. This lesson covers the essential DBA tasks that keep Oracle Database running reliably.

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ARCHIVELOG vs NOARCHIVELOG Mode

Mode	Description	Recovery Capability
NOARCHIVELOG	Filled redo logs are overwritten	Only full database restore (no point-in-time recovery)
ARCHIVELOG	Filled redo logs are archived before overwriting	Full point-in-time recovery

-- Check current mode
SELECT log_mode FROM v$database;

-- Switch to ARCHIVELOG mode (requires restart)
SHUTDOWN IMMEDIATE;
STARTUP MOUNT;
ALTER DATABASE ARCHIVELOG;
ALTER DATABASE OPEN;

Tip: Production databases should always run in ARCHIVELOG mode.

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Recovery Manager (RMAN)

RMAN is Oracle's primary backup and recovery tool:

Full Database Backup

rman target /

RMAN> BACKUP DATABASE PLUS ARCHIVELOG;

Incremental Backup

# Level 0 (base backup)
RMAN> BACKUP INCREMENTAL LEVEL 0 DATABASE;

# Level 1 (changes since last level 0 or level 1)
RMAN> BACKUP INCREMENTAL LEVEL 1 DATABASE;

Tablespace Backup

RMAN> BACKUP TABLESPACE users;

Backup Validation

RMAN> RESTORE DATABASE VALIDATE;
RMAN> VALIDATE BACKUPSET 42;