Overview to Oracle 10g RMAN
Posted by appsinfo on February 24, 2009
Overview of the RMAN
Recovery Manager (RMAN) is an Oracle database client which performs backup and recovery tasks on an Oracle database.
The environment for RMAN must include:
- a target database to backed up
- the RMAN client
Optional RMAN components:
- Flash Recovery Area: a disk location in which the database can store and manage files related to backup and recovery
- Media Management Software: required for RMAN to interface with backup devices such as tape drives
- Recovery Catalog Database: a separate database schema used to record RMAN activity against one or more target databases
Is the database which needs to be backed up.
To connect to a target database the password file must exist in ORACLE_HOME/dbs. For more information refer oracle documentation.
RMAN Backup Formats: Image Copies and Backup Sets
RMAN backups can be stored in one of two formats:
- Image Copy
- Backup Set
An image copy is an exact copy of a single datafile, archived redo log file, or control file. Image copies are not stored in an RMAN-specific format. They are identical to the results of copying a file with the UNIX cp command. This is the same as a Cold Backup.
A backup set is a collection of files (called backup pieces) each of which contain the backup to one or more database files. A backup set contains the data from one or more datafiles or archived redo logs, or control files or spfile. Datafiles and archivelogs cannot be mixed together in the same backup set.
Binary Compression of Backup Sets
You can use binary compression to reduce the size of your backup sets. The compression algorithm built into the Oracle server is tuned specifically for efficient compression of Oracle archived logs and datafiles, and will generally yield better compression than general-purpose compression utilities not tuned for Oracle database files.
RMAN is a command-line-oriented database client. From the RMAN client you can issue RMAN commands and SQL statements to perform and report on backup and recovery operations.
The RMAN executable is typically installed in the same directory as the other database executables. On Unix systems, for example, the RMAN executable is located in $ORACLE_HOME/bin.
The RMAN executable is located in $ORACLE_HOME/bin.
RMAN maintains metadata about the target database and its backup and recovery operations in the RMAN repository. The metadata includes:
- the target database schema
- archived redo logs
- all backup files on disk or tape
You can display RMAN repository information with the LIST REPORT and SHOW commands.
RMAN repository data is always stored in the control file of the target database. The CONTROL_FILE_RECORD_KEEP_TIME initialization parameter controls how long backup records are kept in the control file before those records are re-used to hold information about more recent backups. The repository can also be kept in a recovery catalog, a separate database that keeps historical data on backup activities much longer than the control file and preserves backup information if the control file is lost.
Flash Recovery Area
The Automatic Disk-Based Backup and Recovery feature simplifies managing disk space and files related to backup and recovery, by managing all backup and recovery related files in a flash recovery area. You set the flash recovery area size and location, using the DB_RECOVERY_FILE_DEST and DB_RECOVERY_FILE_DEST_SIZE initialization parameters. You also specify a retention policy that dictates when backups may be discarded. RMAN then manages your backup storage, deleting obsolete backups and backups already copied to tape when space is needed, but keeping as many backups on disk as space permits.
In addition to RMAN repository records, the recovery catalog can also hold RMAN stored scripts, sequences of RMAN commands for common backup tasks