|Oracle® Database Backup and Recovery Advanced User's Guide
10g Release 1 (10.1)
Part Number B10734-01
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.
The new features for this release greatly increase the manageability of RMAN, making backup and recovery simpler and more performant.
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
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.
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
DATABASE command, the database uses the flashback logs as well as the archived redo logs to reconstruct its contents at the specified time.
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.
Oracle Database Backup and Recovery Basics to learn how to roll forward image copies
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:
"Tuning Recovery Manager: Overview" to learn more about RMAN performance tuning
RMAN can create datafiles automatically when the user executes
RECOVER commands in the following situations:
Oracle Database Recovery Manager Reference to learn about the behavior of the
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
RESETLOGS statement is now modified so that the database now archives the current online redo logs (if possible) before clearing the logs.
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.
BACKUPCommand Creates Backup Sets or Image Copies
In previous releases, RMAN had two separate commands to back up datafiles:
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,
COPY can copy a database or multiple tablespaces, datafiles, archived logs and datafile copies.
RMAN can create and restore proxy backups of archived redo logs.
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.
If you enable block change tracking, then the database automatically tracks which datafile blocks have changed in change tracking files. When you execute
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.
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.
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.
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
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.
The RMAN command
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).
Oracle Database Recovery Manager Reference to learn about the
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.
"Working with RMAN Stored Scripts in the Recovery Catalog" for the new commands and options
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.
Oracle Database Backup and Recovery Basics for more details on using compressed backupsets.
The PREVIEW option to the RESTORE command can now tell you which backups will be accessed during a RESTORE operation.
Oracle Database Backup and Recovery Basics for more details on RESTORE PREVIEW
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. .
"Managing Backup Windows and Performance: BACKUP... DURATION" for more details on managing backup duration and throttling