What is Recovery Manager (RMAN)
RMAN stands for recovery manager.it is a utility that can manage your entire Oracle backup and recovery activities. it is find in $ORACLE_HOME/bin. It comes with database installation
Usage Without Catalog rman target / With Catalog rman target / catalog <user>/<pass>@catdb
RMAN benefits over Manual Backups
(1)RMAN Backup Saves storage space, because it only backs up blocks that have ever held data.
(2)Eliminates performance overhead during backups, because it doesn’t place oracle tablespace in backup mode.
(3) Helps maintain database integrity by detecting block corruption during backups.
(4)Decreases backup time by allowing parallelized and incremental backups.
(5)Maintains history of old backups and status of running backups.
(6)Has built in reporting capabilities.
(7)Allows transition to 10g Automatic Storage Management which requires RMAN. We can use RMAN with oracle ASM storage based databases
(8) Decreases time for specific types of recoveries by allowing block and tablespace point in time options.
(9) Provides GUI interface when used with OEM.
Media manager software
To store backups on tape, RMAN requires media manager software, a third party software program that writes, reads, and manages sequential media such as tapes to backup and recover data. In the case of backup, RMAN starts the Oracle Server session which reads data and sends it to the media manager which writes the data to the tape device. In the case of restore, the media manager software reads the data from the tape and sends it to the Oracle Server session which restores data to the disk.
The SBT API is the interface through which RMAN interacts with the media manager. The API defines the functions that create backup files, write to/read from the backup media, and search for/remove backup files. Management of backup devices and media is handled by the media manager, and is outside the scope of the SBT API.
The core of the RMAN and media manager software integration is the media management library, supplied by the backup vendor. This library contains an implementation of the SBT API functions, and is linked in with the Oracle server binary. In Oracle 8.1.6 and below versions, the library must be explicitly linked in with the Oracle server binary before starting RMAN. In Oracle 8.1.7, the library is implicitly loaded by the OS on the start of the Oracle server session. In Oracle9i and 10g, the library is automatically loaded when RMAN channels are allocated.Oracle calls these SBT functions to back up and restore data files to and from media controlled by the media manager.
The commom media manager software with RMAN are
RMAN base tables
- RMAN is a powerful tool for taking backup .It maintains all the backup related information in RMAN base tables in RMAN catalog.We are listing all tables and views are which are generated in the catalog database.
- Use the DESCRIBE command for each table or view to display column information.We have given some explanation for each table so that you can understand what data is residing in it