Question: I've been using data pump (the export utility) to backup my database, but I wonder if I should be using RMAN instead. They both do backups, so what's the advantages of each?
Answer: Yes, RMAN and export both backup tables, and they both support flashback database, but there are some important differences:
* Data Pump Export (expdp) - The export utility is a "logical" backup, usually done by specifying specific tables. If you fail to do a "consistent" export, or if you fail to include related tables and use RESTRICTED and CONSISTENT mode (with referential integrity constraints), you may not be able to recover properly. Also, export can only read "cooked" files, and database with raw files (e.g. RAC) cannot be copied with export. Hence, export is often used as a supplement to RMAN, usually for the restore of specific tables.
* Recovery manager (rman) - RMAN is designed for backup and recovery, a extension of the Enterprise Backup Utility (EBU). RMAN reads raw files, takes time-consistent backups. manages referential integrity.
Advantages & disadvantages of Export:
* Free, and easy to use
* Very slow, compared to RMAN (examines every data block)
* Easy restore of a specific table
* Does not require ARCHIVELOG mode
* Export will discover the SCN that is closest to the specified time. This SCN is used to enable flashback with export.
Advantages & disadvantages of RMAN:
* Supports raw devices
* RMAN has block-level media recovery
* Has a catalog for backup tracking and a report utility
* Fast - If you dedicate a backup device for each production disk, you can backup terabytes in the time it takes to backup any single disk.
* Does hot or cold backups
* Backups and restores can be done in parallel
* Allows incremental backups (block change tracking)
* Interfaces with media management systems (TMS)
* RMAN can be used to backup changed data even after a nologging operation, and you can move away from archivelog mode.
by Burleson Consulting - www.dba-oracle.com