Oracle Database 10g Administration (DBA): Backup and Recovery

RMAN Overview

Note: The article ( named RMAN Overview ) was taken from www.in-oracle.com.

RMAN supports both cold and hot backup
Does block level backup and recovery
The RMAN online backup is easier to take than an online user-managed backup
RMAN command language is platform independent
The online backup doesn't put the tablespace in "backup mode", so no extra redo logs are not generated

2. Where does RMAN store the metadata information about the backups ?

In RMAN Catalog Repository (created on a database schema) or in the control files of the target database. Personally, I prefer to use the control file because the result is the same, but there is less administrative work for this.

3. What is RMAN ?

RMAN (Recovery Manager) is the recommended tool for Oracle database backup, restore and recovery operations. RMAN is an Oracle product.

4. Which are the components of RMAN ?

RMAN software: RMAN executable software could be find in $ORACLE_HOME/bin directory
Processes: RMAN creates processes to perform different activities, such as backups, restore and recovery
Target database: The target database is the database RMAN connect to backup, restore, recover information from (in)
Recovery Catalog Database: Store the metadata for the RMAN activities. It doesn't store the backup of the target database. The target control files also could keep the RMAN metadata.
RMAN channel: The RMAN Channel provide a mean of communication between the server and the operating system. Using more channels increase the speed of the RMAN activities.
Backup Set: A Backup Set store one or more physical files or backup pieces. You cannot split a file across different backup sets or mix archived logs and datafiles into one backup set.
Image Copy: Is a replica of the physical files in uncompressed form. Because of this the images copies could be used to restore the data files using RMAN or operating system commands.

5. Which are the advantages of each RMAN metadata repositories ?

RMAN Catalog Repository Advantages Using Control file : Advantages

One repository for many databases
RMAN scripts could be used to manage the RMAN utility
The control files has a normal I/O activity during the RMAN operations
The control files are smaller in size and we don't need to take care of CONTROL_FILE_RECORD_KEEP_TIME initialization parameter

Less administrative tasks
We don't need another instance installation for this

NOTE: CONTROL_FILE_RECORD_KEEP_TIME init.ora parameter must be set to a value no less than the database backup retention period. This parameter applies only to records in the control file that are circularly reusable (such as archive log). It does not apply to records such as data files or tablespaces. You can read the Metalink Note 47322.1.

6. Which are the disadvantages of each RMAN metadata repositories ?

RMAN Catalog Repository Disadvantages	Using Control file : Disadvantages
More administrative tasks We need another instance installation for this	Many repositories for many databases RMAN scripts could NOT be used to manage the RMAN utility The control files has a high I/O activity during the RMAN operations The control files are bigger in size and we need to take care of CONTROL_FILE_RECORD_KEEP_TIME initialization parameter

Note: The article ( named RMAN Overview ) was taken from www.in-oracle.com.

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