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Oracle 1Z0-078 study materials
Oracle 1Z0-078 study resources

Oracle 1Z0-078: Backup and Recovery

Oracle 1Z0-078 · Work through your exam, one topic at a time.

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Backup and Recovery

Backup and Recovery

This domain tests RMAN-based protection: archivelog mode, backup types and strategies, retention policy, restore versus recover, incomplete recovery, and the flashback features that shorten recovery.

Core rules

  • Online consistent backups and point-in-time recovery require ARCHIVELOG mode, enabled from the MOUNT stage with ALTER DATABASE ARCHIVELOG.
  • RMAN produces backup sets (default, compressed, can go to disk or tape) or image copies (block-for-block, usable directly by the instance). Only used blocks are backed up.
  • A level 0 backup is the incremental base. A differential level 1 backs up blocks changed since the most recent level 0 or level 1; a cumulative level 1 backs up blocks changed since the most recent level 0 only.
  • Retention is expressed as REDUNDANCY n or RECOVERY WINDOW OF n DAYS. Obsolete backups violate retention; expired backups are missing files RMAN previously recorded.
  • The fast recovery area (DB_RECOVERY_FILE_DEST plus DB_RECOVERY_FILE_DEST_SIZE) holds backups, archived logs and flashback logs; RMAN prunes per policy when space pressure occurs.
  • RESTORE returns files; RECOVER applies redo. Incomplete recovery uses UNTIL TIME, SCN or SEQUENCE and ends with OPEN RESETLOGS, starting a new incarnation.
  • Flashback Database rewinds using flashback logs (DB_FLASHBACK_RETENTION_TARGET); FLASHBACK TABLE uses undo and needs row movement where applicable.

Worked example

Level 0 on Sunday; blocks change on Monday and Tuesday; a differential level 1 runs each night. Tuesday's differential backup contains Tuesday's changes only (the Monday level 1 is its reference), so recovery needs Sunday level 0, Monday level 1, then Tuesday level 1. Switching Monday and Tuesday to cumulative means Tuesday's backup contains Monday plus Tuesday changes, so Sunday level 0 plus Tuesday cumulative suffices - fewer files to restore, more backup volume.

Traps that cost marks

  • Assuming a Tuesday differential includes Monday's changes.
  • Deleting archived logs at OS level, breaking the catalog and retention bookkeeping.
  • Treating REDUNDANCY 1 as protection against losing the only copy to the same disk failure.