11g Data Guard Real
Time Queries and
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
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
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:
DATABASE RECOVER TO LOGICAL STANDBY KEEP IDENTITY;
KEEP IDENTITY clause
DBID of the primary
database. Once completed the database can be converted back to
a physical standby database.