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This article mainly extracts some relevant knowledge from the official Oracle 11g Data Guard Concepts and Administration and other materials to help understand the architecture of Data Guard.

RAC 11.2 Architecture (3) http://blog.csdn.net/wildwave/article/details/6882567 also discusses some concepts about Data Guard, here, the repetition will be skipped

New features of Oracle Data Guard 11.2

New features common to Redo apply and SQL Apply A Data Guard configuration can consist of one main library and up to 30 standby libraries, eliminating the need for the FAL_CLIENT initialization parameter Oracle ASM and the default archive path used by the fast recovery region feature from LOG_ARCHIVE_DEST_10 to compression of LOG_ARCHIVE_DEST_1Redo transmissions is no longer limited to use when solving gap, when compression is specified in a destination All redo data sent to that destination is compressed and a new ALTER SYSTEM FLUSH REDO expression is added. On failover, the SQL statement can flush undelivered redo logs from a master database in mounted state to an standby database, so that no data loss can be achieved when the main database is not running in zero data loss protection mode.

New features of Redo Apply you can use the STANDBY_MAX_DATA_DELAY parameter to set the maximum allowable delay time in a real-time query environment. You can use the ALTER SESSION SYNC WITH PRIMARY statement to ensure that the physical standby database synchronizes with the main database V $DATAGUARD_STATS view is more accurate in many fields. Including apply lag and transport lag, you can view the histogram of applying delay values on the physical standby by querying the new view V$STANDBY_EVENT_HISTOGRAM. In real-time query mode, the bad block in the main database is automatically replaced by the copy of the block on the physical standby database. And vice versa.

SQL Apply's new features logical standby and LogMiner tools support tables that use basic table compression, OLTP table compression, and mixed column compression (mixed column compression is one of the features of Oracle Exadata) logical standby and LogMiner tools support tables with SecureFile LOB fields. Compression and encryption on the SecureFile LOB field are also supported. (deduplication (De-duplication) and fragment-based (fragment-based) operations are not supported) changes that occur in the context of XA (Extended Architecture) global transactions on the Oracle RAC primary database are replicated on the logical standby database. Online redefinitions performed on the master database using the DBMS_REDEFINITION package are copied to the logical standby database logical standby supports version use in the master database, including upgrading applications using version-based redefinitions, thereby minimizing downtime (details on version-based redefinition edition-based redefinition can be seen in Oracle Database Advanced Application Developer's Guide) the logical standby database supports stream capture. This feature allows you to uninstall one-way information propagation from the main library and use logical standby as a hub to propagate information to multiple databases. Stream capture can also propagate local changes to a logical standby database

New features in Oracle Data Guard 11.1

New features common to Redo apply and SQL Apply

Redo traffic compression. When redo gap occurs, the redo is compressed before it is transmitted over the network to improve transmission performance Redo transmission response time histogram. The V$REDO_DEST_RESP_HISTOGRAM view contains a histogram of the response time of the destination for each SYNC redo transmission. The data in the view can help you determine the appropriate value of the NET_TIMEOUT attribute in LOG_ARCHIVE_DEST_n faster role switching validates the redo transport network session (through SSL) and simplifies the Data Guard management interface. DB_UNIQUE_NAME is enhanced by abandoning some redundant SQL expressions and initialization parameters. A column of PRIMARY_DB_UNIQUE_NAME has been added to V$DATABASE to query the DB_UNIQUE_NAME of the main library. There is no communication between databases with the same DB_UNIQUE_NAME in 11g. Use the physical standby database for rolling upgrades. Rolling upgrades of diversified Data Guard configurations are achieved by adding the KEEP IDENTITY option to ALTER DATABASE RECOVER TO LOGICAL STANDBY to temporarily convert the physical standby database into logical standby. This feature allows mixed use of Linux and Windows primary and standby libraries in the same Data Guard configuration

New features of Redo Apply

Real-time query function of physical standby Snapshot standby uses physical standby to detect write loss (lost-wirte detection) strengthens the integration with RMAN

New features of SQL Apply

More object data types and PL/SQL packages are supported. (storing XML;DBMS_RLS;DBNS_GFA in CLOB) supports transparent data encryption (TDE) uses DBMS_LOGSTDBY.APPLY_SET packages to dynamically set SQL Apply parameters when using logical standby databases, switchover's support for RAC is enhanced. No need to close any instances enhances the DDL processing power of SQL Apply. Parallel execution of parallel DDL creates scheduling tasks on the standby database using the DBMS_SCHEDULER package

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