New Features in 11g on Backup and Recovery

1. Block change tracking in standby.

         Now incremental backups can be faster now in standby database by enabling the block change tracking in it.

2. Active Database Duplication

   Now in 11g we can directly duplicate a database over the network without having to back up and provide the source database files. This direct database duplication is called active database duplication. It can be done either with Database Control or through RMAN. Instance that runs the duplicated database is called auxiliary instance.

3. Archived Redo Log Failover

When backing up archived redo logs RMAN only includes a single copy of each archived redo log, regardless of how many archive log destinations are being written to. The Oracle 11g archived redo log failover feature allows RMAN to complete a backup provided at least one valid copy of each archived redo log is present in one of the specified archive destinations. If RMAN finds a log file containing corrupt blocks, it searches the other archive destinations for a valid copy to back up.

4. Archived Log Deletion Policy Enhancements

The extended syntax allows for configurations where logs are eligible for deletion only after being applied to, or transferred to, one or more standby database destinations.

ARCHIVELOG DELETION POLICY {CLEAR | TO {APPLIED ON [ALL] STANDBY |

  BACKED UP integer TIMES TO DEVICE TYPE deviceSpecifier |

  NONE | SHIPPED TO [ALL] STANDBY}

  [ {APPLIED ON [ALL] STANDBY | BACKED UP integer TIMES TO DEVICE TYPE deviceSpecifier |

  NONE | SHIPPED TO [ALL] STANDBY}]...}

5. Multisession Backups

A file section is defined as a contiguous range of blocks from a single file. The SECTION SIZE parameter in the BACKUP command tells RMAN to create a backup set where each backup piece contains the blocks from one file section, allowing the backup of large files to be parallelized across multiple channels.

The following example of a multisection backup sets the parallelism to 4, allowing a tablespace with a single 1000M datafile to be backed up in 4x250M sections.

# One-off configuration of device type and parallelism.

CONFIGURE DEVICE TYPE sbt PARALLELISM 4;

CONFIGURE DEFAULT DEVICE TYPE TO sbt;

# Backup large tablespace in 4 sections.

RUN {

  BACKUP SECTION SIZE 250M TABLESPACE my_1000M_ts;

}

Some points to remember about multisection backups include:

• If the section size is larger than the file size, RMAN does not use a multisection backup for the file.
• If the section size is so small that more than 256 sections would be produced, RMAN increases the section size such that 256 sections will be created.
• SECTION SIZE and MAXPIECESIZE cannot be used together.
• A backup set never contains a partial datafile, regardless of whether or not it is a multisection backup.

6. Optimized Backing Up of Undo Data

In Oracle Database 11g, during a backup, the committed data isn’t backed up, thus leading to a saving of storage space as well as faster backups for large OLTP-type databases. Since the new optimized undo backup is automatically enabled, you don’t have to configure anything special to take advantage of this feature.

7. Enhanced Block Media Recovery

In Oracle Database 11g, there is a new command to perform block media recovery, named the recover ... block command replacing the old blockrecover command. The new command is more efficient since because it searches the flashback logs for older uncorrupted versions of the corrupt blocks. This requires the database to work in archivelog mode and has the Database Flashback enabled.

If flashback logs are present, RMAN will use these in preference to backups during block media recovery (BMR), which can significantly improve BMR speed.

8. Backup of Read-Only Transportable Tablespaces:

   In previous versions of Oracle, transportable tablespaces could only be backed up if they were in read/write mode. It is now possible to backup read-only transportable tablespaces.

  9.       Data Recovery Advisor

       Data Recovery Advisor is a built-in tool to automatically diagnose data failures and recommend repairs. You 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.

10. 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, you 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). You can use some of the logical flashback features with a flashback data archive to access data from far in the past.

11.      Data Block Corruption Prevention and Detection Parameters:

            In Oracle Database 11g, several database components and utilities in addition to RMAN can detect a corrupt block and record it in the view "V$DATABASE_BLOCK_CORRUPTION". Oracle Database automatically updates this view when block corruptions are detected or repaired. The benefit is that the time it takes to discover block corruptions is shortened.

           

12.         Online Patching:

           

            Initially available for Linux, this allows certain diagnostic patches to be installed in a completely online manner, i.e. without requiring the database to be brought down and applications to be disconnected.

Regards
~ Nv