Oracle Recovery Manager (RMAN)

Oracle Recovery Manager satisfies the most pressing demands of performant, manageable backup and recovery, for all Oracle data formats.

A complete high availability and disaster recovery strategy requires dependable data backup, restore, and recovery procedures. Oracle Recovery Manager (RMAN), a command-line and Enterprise Manager-based tool, is the Oracle-preferred method for efficiently backing up and recovering your Oracle database. RMAN is designed to work intimately with the server, providing block-level corruption detection during backup and restore. RMAN optimizes performance and space consumption during backup with file multiplexing and backup set compression, and integrates with Oracle Secure Backup and third party media management products for tape backup.

RMAN takes care of all underlying database procedures before and after backup or restore, freeing dependency on OS and SQL*Plus scripts. It provides a common interface for backup tasks across different host operating systems, and offers features not available through user-managed methods, such as parallelization of backup/recovery data streams, backup files retention policy, and detailed history of all backups.

Overview of RMAN Functional Components

The RMAN environment consists of the utilities and databases that play a role in backing up your data. At a minimum, the environment for RMAN must include the following:

• The target database to be backed up
• The RMAN client, which interprets backup and recovery commands, directs server sessions to execute those commands, and records your backup and recovery activity in the target database control file.

Some environments will also use these optional components:

• A 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
• A recovery catalog database, a separate database schema used to record RMAN activity against one or more target databases

The following diagram illustrates these components:

New Features in Oracle Database 11g

Data Recovery Advisor
The Data Recovery Advisor is a new tool aimed at reducing a user’s time spent analyzing and formulating a suitable recovery plan for a given failure. A ‘failure’ in the context of the DRA can be a missing, inaccessible, or wrong version of a file (e.g. control file, data file), physical corruptions resulting from I/O errors, or logical block inconsistency. After identifying all current failures, the DRA then recommends the optimal, feasible recovery plan, and if the user desires, automatically executes a selected recovery plan. All DRA functions can be accessed via EM or RMAN’s command-line interface.

Multisection Backups
RMAN can back up or restore a single file in parallel by dividing the work among multiple channels. Each channel backs up one file section, which is a contiguous range of blocks. This speeds up overall backup and restore performance, and particularly for bigfile tablespaces, in which a data file can be sized upwards of several hundred GB to TB's.

Fast Backup Compression
In addition to the Oracle Database 10g backup compression algorithm (BZIP2), RMAN now supports the ZLIB algorithm, which offers 40% better performance, with a trade-off of no more than 20% lower compression ratio, versus BZIP2.

Virtual Private Catalog
A recovery catalog administrator can grant visibility of a subset of registered databases in the catalog to specific RMAN users.

Integration with Windows Volume Shadow Copy Services (VSS)
The Oracle database can participate in the VSS infrastructure on Windows platforms, with compatible backup management applications and storage systems. This feature allows VSS-enabled backup management applications to snapshot the Oracle database and restore at the datafile, tablespace, or database level.

New Features in Oracle Database 10g Release 2

Backup Set Encryption
Backup security is vital to the well-being of any company. Backups should only be able to be opened and read by their creators. With Oracle Database 10gR2, backup sets made to disk can now be encrypted, for the whole database or particular tablespaces, using the new CONFIGURE ENCRYPTION FOR [DATABASE | TABLESPACE …] option.

Unused Block Compression
With unused block compression (enabled by default), only the currently used blocks are read and written during a full backup. This speeds up backups and reduces backup size. In previous releases, blocks that are currently unused, but had been used at some point in the past, were required to continue to be backed up. Also, blocks that have never been used are never backed up.

Dynamic Channel Allocation for RAC Environments
By configuring the PARALLELISM parameter, RMAN will dynamically allocate the specified number of channels across all active RAC nodes, to perform the backup or restore operation. RMAN utilizes Oracle Clusterware (formerly known as Cluster Ready Services) to allocate channels to the least loaded nodes, to perform the operations. In this way, the overall backup or restore workload can be distributed across the RAC nodes more efficiently.

Enterprise Manager Enhancements
Oracle Enterprise Manager, a single, integrated solution for administering and monitoring systems and applications based on the Oracle technology stack, is further enhanced for managing and monitoring backup jobs.

Database Control allows DBAs to view all backup jobs by date range and backup type (e.g. full, datafile, archive log), along with their status (e.g. "completed", "completed with warnings"), input and output sizes, and output rate. Each backup job can be further drilled down to review input files and output backup sets/image copies, their sizes, and compression ratio (if enabled).

Grid Control offers several enhancements to manage backups across the enterprise. Backup jobs can be viewed across all target databases, and a failed job can be easily restarted without having to resubmit the job again. In case a backup job fails, the DBA can be notified immediately via email. In addition, user-defined RMAN scripts can be created as jobs and applied to any number of target databases. The recovery wizard has also been enhanced to allow restore and recovery to a different Oracle home, in the event that the original Oracle home or database is lost.

For Oracle Database 10g Release 1 New Features, refer to this overview.