The concept and architecture of Oracle Rman (i) the concept and architecture of Rman

I. The concept and architecture of Rman

Recovery Manager (RMAN) is an Oracle tool for backup (Backup), restore (Restore), and recovery (recover) databases. Rman can only be used in ORACLE8 or higher versions. It can back up the entire database or database parts, such as tablespaces, data files, control files, archive files, and spfile parameter files. Rman also allows you to perform incremental block-level backups, and incremental Rman backups are time and space efficient because they only back up those blocks that have changed since the last backup. Moreover, with the interface provided by Rman, third party backup and recovery software such as Veritas will provide more powerful backup and recovery management capabilities.

Rman also provides additional functionality, such as database cloning, the use of Rman to build standby databases, and the use of Rman to back up and move files on raw devices (raw) to become easier and simpler. The 9i Rman will make backup and recovery work faster and more perfect through enhanced automatic configuration and management capabilities, as well as a unique block-level recovery. The 9i Rman has the following characteristics:

• Automated backup and recovery

• Convenient Backup archive logs

• Automatic detection of new data files

• Support for incremental backups

• Minimize backup and recovery errors

• Reduced time to recover

• No additional redo logs are generated in hot backups

• Automatic detection of decomposed data blocks

• Parallel backup and recovery operations

• Table space is not placed in Backup mode when online backup

As you can see, in some of the above features, shows the powerful features and benefits of Rman, because Rman is a block-level backup and recovery, backup and recovery occurs at the database block level, you can get consistent chunks of data by comparing blocks of data, and you can avoid backing up blocks that are not used. Block-level problems can be tested for block decay.

The Rman architecture is described below:

1. RMAN Tools

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The Rman command, originating from ORACLE version 8, is typically located in the $oracle_home/bin directory and can be used to start the Rman tool by running the Rman command to back up and restore the interface.

2. Service Process

The Rman service process is a background process for communication with the Rman tool and the database, and also for the communication between the Rman tools and the I/O settings such as disk/tape, and the service process is responsible for all the work of backup and recovery and will produce a service process as follows

• When connecting to the target database

• Allocation of a new channel

3, Channel

A channel is a way to read and write before a service process and an I/O device one channel will correspond to a service process, when allocating channel, need to consider I/O device type, I/o concurrency processing ability, I/O device can create file size, database file maximum read rate, maximum number of open files and other factors

4. Target Database

is Rman for backup and recovery of the database, Rman can back up in addition to the online log, pfile, password files outside the data files, control files, archive logs, SPFile

5, restore the directory

A database used to hold backup and recovery information, not recommended for creation on the target database, the recovery directory allows you to manage multiple target databases at the same time, store more backup information, and store backup scripts. If the recovery directory is not used, the control file can be used instead of the recovery directory, Oracle 9i because the control file automatic backup function, the use of control files to a large extent can replace the recovery directory.

6, the Media management layer

Media Management Layer (MML) is a third-party tool or software that is used to manage tape-reading and file tracking management. If you want to back up to tape directly through Rman, you must configure the media management layer, and media management tools such as backup software can invoke Rman for backup and recovery.

7. Backup, backup set and backup slice

When the backup command is issued, RMAN creates a completed backup containing one to more than one backup set, which is a logical structure containing a set of physical files. These physical files are the corresponding backup slices. A backup slice is the most basic physical structure that can be generated on a disk or tape and can contain data files, control files, archive logs, and SPFile files for the target database.

Backup sets and backup slices have the following provisions:

(1) A data file cannot span a backup set, but can span a backup slice

(2) Data files, control files can be saved on the same backup set, but can not be saved with the archive log on the same backup set