What's New in Backup and Recovery?

This section describes new features of Recovery Manager in Oracle Database Release 10g and provides pointers to additional information. For information on new features in Oracle9i and previous releases, refer to the documentation for those releases.

Oracle Database Release 10g New Features in Backup and Recovery

The new features for this release greatly increase the manageability of RMAN, making backup and recovery simpler and more performant.

• Flash Recovery Area

  A flash recovery area is a directory, file system, or Automatic Storage Management disk group that serves as the default storage area for files related to recovery. Such files include

  • Multiplexed copies of the control file and online redo logs
  • Archived redo logs and flashback logs
  • RMAN backups
  • Files created by RESTORE and RECOVER commands

  Recovery components of the database interact with the flash recovery area to ensure that the database is completely recoverable using files in the flash recovery area. The database manages the disk space in the flash recovery area, and when there is not sufficient disk space to create new files, the database creates more room automatically by deleting the minimum set of files from flash recovery area that are obsolete, backed up to tertiary storage, or redundant.

  See Also: Oracle Database Backup and Recovery Basics to learn how to set up the flash recovery area "Configuring the Flash Recovery Area: Advanced Topics"

• Oracle Flashback Database

  With the FLASHBACK DATABASE command, you can quickly revert a database to a previous time--without restoring datafiles and performing media recovery. When you enable the Flashback Database feature, the database automatically creates, deletes, and manages flashback logs inside the flash recovery area. When you run the FLASHBACK DATABASE command, the database uses the flashback logs as well as the archived redo logs to reconstruct its contents at the specified time.

  See Also: "Oracle Flashback Database: Alternative to Point-In-Time Recovery"

• Incrementally Updated Backups: Rolling Forward Image Copies

  You can apply backup incrementals to datafile image copies--not current datafiles--to roll them forward to a specified point in time. In this way, you can potentially reduce recovery time by applying incrementals to copies and avoid taking a full image copy again after incremental backups.

  See Also: Oracle Database Backup and Recovery Basics to learn how to roll forward image copies

• Disk Topology and Automatic Performance Tuning

  The new disk topology API extends RMAN's capability to more platforms and file types. RMAN is also able to tune its parameters automatically according to disk topology information, which decreases the degree of user intervention required for performance tuning. RMAN can automatically tune the following:

  • The contents of the backup sets that define which files are multiplexed
  • The level of multiplexing
  • The number and size of the input and output disk buffers

    See Also: "Tuning Recovery Manager: Overview" to learn more about RMAN performance tuning

• Automatic Datafile Creation

  RMAN can create datafiles automatically when the user executes RESTORE or RECOVER commands in the following situations:

  • The control file has metadata for the datafile, that is, the control file was backed up after datafile creation, but the datafile itself is not backed up.
  • The control file does not have metadata for the datafile, that is, the user did not back up the control file after datafile creation.

    See Also: Oracle Database Recovery Manager Reference to learn about the behavior of the RECOVER command

• Recovery Through Resetlogs

  RMAN simplifies recovery with backups taken from an earlier incarnation so that it is as easy as recovering a backup from the same incarnation. Hence, you no longer need to make new backups of a database after a RESETLOGS. The procedure is as easy and transparent as recovering a backup from the same incarnation. Also, the ALTER DATABASE OPEN RESETLOGS statement is now modified so that the database now archives the current online redo logs (if possible) before clearing the logs.

  See Also: "Point-in-Time Recovery to a Previous Incarnation"

• Restore Failover

  If a backup piece is inaccessible or corrupted, then RMAN can automatically fail over to another copy of this backup piece during RESTORE. If all copies of this backup set are unusable, then RMAN can fail over to previous redundant backup sets. RMAN continously fails over to previous backups until it exhausts all possibilities. This feature is similar to archived log failover.

  See Also: "Restore Failover" for details of restore failover behavior. Oracle Database Recovery Manager Reference to learn about the behavior of the RESTORE command

• BACKUP Command Creates Backup Sets or Image Copies

  In previous releases, RMAN had two separate commands to back up datafiles: BACKUP and COPY. The BACKUP command backed up the datafile into a backup set, which is a proprietary format that allows multiple datafiles to be multiplexed together. The COPY command generated image copies, that is, bit-by-bit copies of datafiles.

  Starting in Release 10g, the COPY command is deprecated in favor of an enhanced BACKUP command that enables you to specify whether RMAN should create copies or backup sets. As a result, BACKUP AS COPY can copy a database or multiple tablespaces, datafiles, archived logs and datafile copies.

  See Also: Oracle Database Backup and Recovery Basics to learn how to copy files Oracle Database Recovery Manager Reference to learn about the output of the BACKUP command

• Proxy Archived Log Backups

  RMAN can create and restore proxy backups of archived redo logs.

• Cataloging Backup Pieces

  Users can now catalog user-specified backup pieces with the CATALOG command. Cataloging a backup piece adds it to the RMAN repository so that it is available for use in recovery operations. This enhanced functionality is useful when you make a copy of a backup piece with an operating system utility, or when you move a backup piece from one disk to another so that it has a different absolute path name.

  See Also: Oracle Database Backup and Recovery Basics to learn how to catalog backup pieces, and Oracle Database Recovery Manager Reference for CATALOG syntax

  
  
  
• Fast Incremental Backups

  If you enable block change tracking, then the database automatically tracks which datafile blocks have changed in change tracking files. When you execute BACKUP INCREMENTAL, RMAN uses the change tracking file to more quickly identify the blocks changed since the previous incremental backup. As a result, RMAN creates incremental backups much faster than in prior releases.

  See Also: Oracle Database Backup and Recovery Basics to learn how to enable block change tracking and manage the change tracking file

  
  
  
• Channel Failover

  If multiple channels are allocated for a BACKUP command, and if RMAN encounters a retriable error (for example, an unplanned instance shutdown in RAC, or a media management error), then RMAN attempts to move the backup to a different channel and complete the work.

  See Also: "Channel Failover"

• Deferred Error Reporting

  For most RMAN commands, RMAN will report errors in the output when they occur and then continue to execute the command if possible. If RMAN can retry a job step on another channel, then it will report a message to this effect. If some job steps could not be completed, then the error stack at the end of command execution will display errors for failed steps.

• Improved RMAN Reporting Through V$ Views

  The V$RMAN_OUTPUT memory-only view shows the output of a currently executing RMAN job, whereas the V$RMAN_STATUS control file view indicates the status of both executing and completed RMAN jobs. The V$BACKUP_FILES provides access to the information used as the basis of the LIST BACKUP and REPORT OBSOLETE commands.

• Automatic Instance Creation for RMAN TSPITR

  RMAN can create an auxiliary instance automatically when you perform RMAN TSPITR. RMAN creates the auxiliary instance in the same machine as the target database. RMAN provides intelligent defaults for the instance, but you can provide nondefault initialization parameters if desired. RMAN automatically dismantles the auxiliary database and instance after a successful TSPITR.

  See Also: "RMAN Tablespace Point-in-Time Recovery (TSPITR)"

• Cross-Platform Tablespace Conversion

  The RMAN command CONVERT TABLESPACE enables you to transport a tablespace from a database running on one platform (for example, Solaris) to a database running on a different platform (for example, Windows).

  See Also: Oracle Database Recovery Manager Reference to learn about the CONVERT command

• Enhanced Stored Scripts Commands

  The recovery catalog now supports global stored scripts, which can be applied to any database in the recovery catalog. A number of new commands have been added to allow for easier manipulation and displaying of stored scripts from the recovery catalog.

  See Also: "Working with RMAN Stored Scripts in the Recovery Catalog" for the new commands and options

  
  
  
• Binary Compression of Backup Sets

  RMAN can now write backup sets in a format that uses binary compression to reduce backup set size. Using compressed backup sets can save storage space, as well as network bandwidth when backing up across a network.

  See Also: Oracle Database Backup and Recovery Basics for more details on using compressed backupsets.

  
  
  
• Enhanced Reporting: RESTORE PREVIEW

  The PREVIEW option to the RESTORE command can now tell you which backups will be accessed during a RESTORE operation.

  See Also: Oracle Database Backup and Recovery Basics for more details on RESTORE PREVIEW

  
  
  
• Managing Backup Duration and Throttling

  The BACKUP command now accepts a DURATION clause, which lets you specify limited time windows for backup activities and minimize load imposed by backup activities during those backup windows. .

  See Also: "Managing Backup Windows and Performance: BACKUP... DURATION" for more details on managing backup duration and throttling