DBA Tips Archive for Oracle

  


Introduction to RMAN

by Jeff Hunter, Sr. Database Administrator


Contents

  1. Overview
  2. What does an RMAN environment look like?



Overview

Let's start by first defining what RMAN is? RMAN, (Recovery Manager), is an Oracle utility used to backup, restore, and recover database files. RMAN is a feature that is automatically included with the database - no separate installation or license is necessary.

RMAN is a client/server architecture that utilizes database server sessions to perform all backup and recover operations. (Similar to the way in which a typical client application accesses the database.) It stores metadata about its operations in the control file of the target database and, optionally, in a recovery catalog schema in an Oracle database.

You can use RMAN from either the command-line or from within the Enterprise Manager GUI.

This article presents a breif introduction into the features of RMAN included with Oracle9i and several examples of using RMAN through the command-line utilities. All examples will utilize an Oracle9i database. It is important to keep in mind that RMAN was introduced with Oracle 8.0 and is not compatible with Oracle databases prior to version 8.0.



What does an RMAN environment look like?

An RMAN environment consists of a set of command-line tools and databases that all play a role in your backup and recovery strategy. The following is a list of components that comprise an RMAN environment:

As stated above, only the RMAN exectables and the target database are required components. Since RMAN always stores its metadata in the target database control file, the recover catalog is optional. It is in your best interest, however, to maintain a recover catalog database for all databases in your enterprise and to host it on a seperate database server than the target databases it is backing up. You don't want to loose your production database AND the recovery metadata that will be used to restore and recovery your database.

RMAN Executable

All of the RMAN executables are automaticall installed with the Oracle RDBMS software and are located in the $ORACLE_HOME/bin directory. The executable is named rman and can simply be started from the command-line as follows:

% rman

Target database

The target database is the database that you are backing up, restoring, or recovering with RMAN. Keep in mind that you can use a single recovery catalog (see below) that contains multiple target databases.

RMAN Repository

The RMAN repository is an optional component and is used to store metadata that RMAN uses to store information about the target database and its backup and recovery operations. Amoung other things, RMAN stores information about:

You can use the LIST, REPORT, and SHOW commands within the RMAN interface in order to access information in the recovery catalog (the metadata either in the control file or the recovery database). You can also use SELECT queries on the catalog views (only if you are using a recovery catalog.)

Again, you can either use a recovery catalog in which to store the repository, or let RMAN store the repository exclusively in the target database control file.

NOTE: Like already mentioned, RMAN needs to store information (metadata) about backup and recovery operations. This is always done in the control file of the target database. RMAN also provides for an optional recovery catalog (an Oracle database / schema) for storing this metadata. In smaller shops, the overhead of maintaining a separate Oracle database for the sole purpose of the recovery catalog is simply a waste of resources. With the autocontrolfile backup feature, it is possible to use the controlfile backups for a recovery catalog. Examples will be provided later in this article that provides the instructions for how to perform this type of backup.

Media Management Interface

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Last modified on
Thursday, 04-Dec-2003 00:00:00 EST
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