11g Data Guard Real Time Queries and Rolling Upgrades Oracle 11g New Features Tips by Donald BurlesonJune 29, 2015

Oracle 11g New Features Tips

Data Guard has been around for the past few major releases and enables zero data loss disaster recovery.  Data Guard is most often used for site failures, as opposed to storage failures, human errors or corruption.  As site failures do not happen on a regular occurrence these disaster recovery (DR) servers can be sitting idle for long periods of time without any use or value being obtained.  Prior to 11g businesses were unable to benefit as greatly from their DR investment.  Oracle's goal for 11g was to make DR cost effective, better utilize standby resources and allow for easy testing of DR. 

Data Guard is included with the Enterprise Edition of Oracle, but it should be noted that a named user or processor license may need to be purchased for the database.  It's always recommended to check with an Oracle sales rep when adding new options. 

The DBA has several options available for configuring, implementing and managing a Data Guard configuration Oracle Enterprise Manager, Data Guard broker command-line interface (DGMGRL), SQL*Plus commands, and initialization parameters.  Oracle has deprecated redundant SQL commands and initialization parameters to simplify the Data Guard configuration.

Physical Standby + Real-Time Query

Oracle Active Data Guard allows DBAs and users to run real-time queries on a physical standby system for reporting and other purposes while still seeing transactional consistent results.  As opposed to previous versions where applying of logs had to stop while reporting was taking place, it now runs simultaneously.  Oracle versions 9 and 10 couldn't have the physical standby in readable state;11g has this and is fully synced.  This ability makes an organizations DR investment much more valuable.  This capability is known as Real-Time Query. 

% While Data Guard is available as an integrated feature of the Oracle Database         (Enterprise Edition) at no extra cost, a license must be purchased for Oracle         Active Data Guard in order to take advantage of Real-Time Query.

A common question of Physical Standby Database with Real Time Query is whether Oracle will deprecate Logical Standby Database.  While a Physical Standby Database can facilitate real-time reporting just as Logical Standby provides, it does serve a different purpose.  With Logical Standby the DBA can add additional indexes, materialized views, global temporary tables, etc., to improve performance for reporting on the standby database.  Also, while Physical Standby handles all data types it is not as flexible as Logical Standby.

Use of physical standby database for rolling upgrades

To further leverage the physical standby system with 11g the DBA can perform rolling upgrades by temporarily converting the physical standby to a logical in order to perform the upgrade. 

While this was available in 10g, it was more manually intensive for the DBA.  Another advantage this new features provides is there is no longer a need for a separate logical standby system to test the upgrade.  The following command would temporarily convert the physical standby to a logical:

SQL> ALTER DATABASE RECOVER TO LOGICAL STANDBY KEEP IDENTITY; 

The KEEP IDENTITY clause retains the DB_NAME and DBID of the primary database.  Once completed the database can be converted back to a physical standby database.