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Oracle Data Guard 11g

By: hitechwriter

Data Guard 11g has been made even more simpler and straightforward to implement and manage using either the Data Guard broker command line interface or Enterprise Manager Grid Control. It has new ways to detect corruptions that avoid data loss and extended down time. Data Guard 11g includes flexible configuration options for fast, automatic failover in both Maximum Availability and Maximum Performance protection modes. Data Guard 11g physical standby databases can offload the primary database of queries and reporting by being open read-only while apply is active, effectively creating a new level of performance protection and return on investment for every Data Guard environment.

Snapshot Standby

This is a new type of standby database that is created from a physical standby database. Once created, a snapshot standby can be opened read-write to process transactions that are independent of the primary database for test or other purposes. A snapshot standby will continue to receive and archive updates from the primary database, however, redo data received from the primary will not be applied until the snapshot standby is converted back into a physical standby database and all updates that were made to it while it was a snapshot standby are discarded.

Failover enhancements

Data Guard 10g Release 2 introduced automatic failover using the new feature Fast-Start Failover with Maximum Availability protection mode (SYNC). Data Guard 11g extends Fast-Start Failover support Maximum Performance mode (ASYNC) by adding a user configurable data loss threshold that guarantees an automatic failover will never result in data loss that exceeds the desired recovery point objective (RPO).

Users can also configure an automatic failover to occur immediately without waiting for the Fast-Start Failover threshold time period to expire based on designated health check conditions or any desired ORA-nnnnn error
Enhanced data protection
A Physical Standby can detect lost data file writes caused by faulty storage hardware and firmware that lead to data corruption on either the primary or the standby database. Data Guard will compare versions of blocks on the standby with that of the incoming redo stream. If there is a version discrepancy it implies a lost write. The user can then failover to the standby database and restore data consistency.

Transient Logical Standby

Users can convert a physical standby to a transient logical standby database to effect a rolling database upgrade, and then revert the standby to its original state as a physical standby database once the upgrade is complete - using the KEEP IDENTITY clause. This benefits physical standby users who wish to execute a rolling database upgrade without investing in redundant storage otherwise needed to create a logical standby database.

Improved Data Guard Broker

Fast-start failover enhancements
Fast-start failover for a configuration operating in maximum performance mode
Allows fast-start failover to be enabled in a Data Guard broker configuration operating in maximum performance mode. The administrator can choose the maximum amount of data that may be lost if a fast-start failover is initiated.
o New DBMS_DG PL/SQL package

The DBMS_DG PL/SQL package allows applications to notify the observer process to initiate a fast-start failover to the target standby database.

o Fast-start failover for configurable conditions
Fast-start failover can be configured to occur when specific database conditions are detected. Certain conditions detectable through the database health-check mechanism and errors raised by the Oracle server (such as ORA errors) may be designated as conditions under which a fast-start failover should occur.
• Manageability enhancements
o Support for snapshot standby databases
o Support for Redo Apply on physical standby databases opened for read
o Improved support for redo transport options. Enables the administrator to specify a connect descriptor for Redo Transport Services.
o Elimination of database downtime when changing the protection mode to and from maximum availability and maximum performance
o Allow a primary or logical standby database in a Data Guard Broker configuration to be mounted without having to be opened automatically
o The DGMGRL CLI ADD DATABASE command can import a pre-configured service attribute from a LOG_ARCHIVE_DEST_n parameter when adding a standby database to the configuration.
o Simplification of the database states managed by the broker. A primary database can be in either the TRANSPORT-OFF or TRANSPORT-ON state. A standby database can be in either the APPLY-OFF or APPLY-ON state.
Compression of redo traffic over the network in a Data Guard configuration
This feature improves the network bandwidth utilization in a Data Guard configuration by compressing archived redo logs as they are transmitted over the network to standby databases, when the log is sent to satisfy a gap at a standby database.
Better integration with the database recovery area because you can now specify
USE_DB_RECOVERY_FILE_DEST as the value for the AlternateLocation and StandbyArchiveLocation database configurable properties.

For more information you can view at Oracle Data Guard

Article Source: Main Articles

ORACLE DATA GUARD guide

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