Wednesday, April 20, 2011

What's New in Backup and Recovery ?

The new features of rman in oracle 11g greatly improve the manageability of Oracle Database backup and recovery. In particular, manageability is increased by the introduction of Data Recovery Advisor, better integration of RMAN with Data Guard, expansion of the recovery catalog functionality, and improved management of archived redo logs.
The new features in this release include:

1.) Data Recovery Advisor :  Data Recovery Advisor is a built-in tool to automatically diagnose data failures and recommend repairs. We can repair failures manually or request that they be repaired automatically. Data Recovery Advisor supports the LIST FAILURE, CHANGE FAILURE, ADVISE FAILURE, and REPAIR FAILURE commands.

2.) Improved integration with Data Guard  :  We can now set persistent RMAN configurations for a primary or physical standby database when RMAN is not connected as TARGET to the database. RMAN works seamlessly on all databases in the Data Guard environment, enabling us to use backups made on one database for restore and recovery on another database. The same recovery catalog can manage metadata for all primary and standby databases.

3.) Improved handling of long-term backups :  We can create a long-term or archival backup with BACKUP ... KEEP that retains only the archived log files needed to make the backup consistent.

4.) Backup failover for archived redo logs in the flash recovery area :  When backing up archived redo log files located in the flash recovery area, RMAN can fail over to archiving destinations outside the recovery area. RMAN can use an intact copy of an archived log in an alternative location to continue writing backups when a log in the recovery area is missing or corrupted.

5.) Archived log deletion policy enhancements :  When we CONFIGURE an archived log deletion policy, the configuration applies to all archiving destinations, including the flash recovery area. Both BACKUP ... DELETE INPUT and DELETE ... ARCHIVELOG obey this configuration, as does the flash recovery area. We can also CONFIGURE an archived redo log deletion policy so that logs are eligible for deletion only after being applied to or transferred to standby database destinations. We can set the policy for mandatory standby destinations only, or for any standby destinations.

6.) Network-enabled database duplication without backups  We can use the DUPLICATE command to create a duplicate database or physical standby database over the network without a need for pre-existing database backups. This form of duplication is called active database duplication.

7.) Recovery catalog enhancements :  The owner of a recovery catalog can GRANT or REVOKE access to a subset of the catalog to other database users in the same recovery catalog database. This subset is called a virtual private catalog. We can also use IMPORTCATALOG command to merge one recovery catalog (or metadata for specific databases in the catalog) into another recovery catalog.

8.) Multisection backups :  RMAN can back up a single file in parallel by dividing the work among multiple channels. Each channel backs up one file section. We create a multisection backup by specifying SECTION SIZE on the BACKUP command. Restoring a multisection backup in parallel is automatic and requires no option. We can parallelize validations of a file with VALIDATE ... SECTION SIZE.

9.)  Undo optimizationThe BACKUP command does not back up undo that is not needed for recovery of a backup. Undo is not needed if it was generated for a transaction that has already committed. This undo can represent the majority of undo in the database.

10.) Improved block media recovery performance  :  When performing block media recovery, RMAN automatically searches the flashback logs, if they are available, for the required blocks before searching backups. Using blocks from the flashback logs can significantly improve block media recovery performance.

11.) Improved block corruption detection  :  Several database components and utilities, including RMAN, can now detect a corrupt block and record it in V$DATABASE_BLOCK_CORRUPTION. When instance recovery detects a corrupt block, it records it in this view automatically. Oracle Database automatically updates this view when block corruptions are detected or repaired. The VALIDATE command is enhanced with many new options such as VALIDATE ... BLOCK and VALIDATE DATABASE.

12.) Faster backup compression  :  In addition to the existing BZIP2 algorithm for binary compression of backups, RMAN also supports the ZLIB algorithm. ZLIB runs faster than BZIP2, but produces larger files. ZLIB requires the Oracle Advanced Compression option. We can use the CONFIGURE COMPRESSION ALGORITHM command to choose between BZIP2(default) and ZLIB for RMAN backups.

13.) Block change tracking support for standby databases We can enable block change tracking on a physical standby database. When We back up the standby database, RMAN can use the block change tracking file to quickly identify the blocks that changed since the last incremental backup.

14.) Improved scripting with RMAN substitution variables  : We can create RMAN command files and stored scripts that accept user input at runtime. Thus, backup scripts can use RMAN substitution variables for tags, filenames, restore point names, and so on.

15.) Integration with VSS-enabled applications  : The Oracle VSS writer is integrated with applications that use the Volume Shadow Copy Service (VSS) infrastructure on Windows. We can use VSS-enabled software and storage systems to back up and restore an Oracle database. A key benefit is the ability to make a shadow copy of an open database.

16.) Lost write detection  We can enable the DB_LOST_WRITE_PROTECT initialization parameter to detect a lost write during managed recovery of a standby database or media recovery of a primary database. Lost write detection is disabled by default.

17.) Backup of read-only transportable tablespaces   :  In previous releases, RMAN could not back up transportable tablespaces until they were made read/write at the destination database. Now RMAN can back up transportable tablespaces when they are not read/write and restore these backups.

18.) Backup and recovery enhancements in Oracle Enterprise Manager : Enterprise Manager includes an interface for Data Recovery Advisor.

19.) Oracle Flashback Transaction : We can reverse a transaction. Oracle Database determines the dependencies between transactions and in effect creates a compensating transaction that reverses the unwanted changes. The database rewinds to a state as if the transaction, and any transactions that could be dependent on it, never occurred.

20.) Flashback data archive A flashback data archive enables the database to automatically track and store all transactional changes to a table for the duration of its lifetime. Thus, we do not need to build this functionality into database applications. A flashback data archive is especially useful for compliance, audit reports, data analysis, and DSS (Decision Support Systems). We can use some of the logical flashback features with a flashback data archive to access data from far in the past.

21.) Improved media recovery performance for databases on SMP systems  : Media recovery of databases on symmetric multiprocessing (SMP) computers is now faster. The performance improvements include the following:
  • More parallelism
  • More efficient asynchronous redo read, parse, and apply
  • Fewer synchronization points in the parallel apply algorithm
  • The media recovery checkpoint at a redo log boundary no longer blocks the apply of the next log.
No configuration is necessary, although we can use new parallel recovery wait events for tuning if the default apply rate is not satisfactory.
For more details of above  points click here


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