Shulou(Shulou.com)06/01 Report--

I. Overview of RMAN

With the help of database server, RMAN realizes the backup of data files, control files, archived log files and database server parameter files. RMAN also allows the use of script files for database backup and recovery, and scripts are saved in the database without the need to write operating system-based script files. The backup files of RMAN are automatically saved in the specified directory, and the names of the files are also maintained by RMAN itself, which reduces the occurrence of human errors in traditional export programs.

II. Characteristics of RMAN

1. Incremental backups are supported. In traditional backup tools such as exp/expdp, only full backup can be achieved, while RMAN can achieve incremental backup, which can reduce the amount of data backed up.

two。 Automatically manage backup files. The data backed up by RMAN is automatically managed by RMAN, including file names, storage directories, automatic identification of recent backup files, and search for backup files needed for recovery.

3. Automated backup and recovery. During backup and restore, you only need to use simple commands, and the execution process is completely maintained by RMAN itself.

4. No redo information is generated. Unlike user-managed online backups, online backups that use RMAN do not produce redo information.

5. Restore the directory. RMAN saves backup and restore scripts in the recovery directory.

6. Image replication is supported. This replication is similar to a user-managed offline backup.

7. The comparison characteristics of the new block. This is the basis of RMAN's support for incremental backups, which makes it possible to skip unused blocks in data files and reduce backup storage space requirements and backup time.

8. Backup data file compression processing. RMAN supports the compression of backup files, and the compressed backup files exist in binary file format, reducing the storage space of backup files.

9. Check the validity of backup files. Verify that the backup files are available before restoring.

III. RMAN system architecture

The above figure is the system structure diagram of RMAN, which can also be understood as a schematic diagram of the information flow of the backup or recovery process. The RMAN executable program starts and establishes a session connection with the database server, and the client issues backup instructions, while the server background process on the database server executes instructions to complete disk read and write operations, and records the backup information in the RMAN information base. The RMAN information base can be saved in the control file on the database side. If you use the recovery directory, the RMAN information base will also be automatically saved in the recovery directory. The metadata of the RMAN recovery directory is obtained from the control file synchronization.

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