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Oracle 11g Snapshot
Standby Database
Oracle 11g New Features Tips by Donald BurlesonJune 29, 2015 |
Oracle 11g New Features Tips
Snapshot Standby is an 11g new feature that has
some interesting applications. One beneficial way to apply
this technology would be if the DBA needs to perform testing, even
potentially destructive testing. Rather than ordering another
server to perform this testing, the DBA could utilize Snapshot
Standby. The DBA would perform the test on the standby.
Then rewind in time to back out changes and then sync to get the
standby current again. Oracle promises with 11g to deliver
higher quality service at lower cost. How is that for cost
savings!
This is different than Flashback Database which
was added in 10g to provide Data Guard a method to correct user
errors. Flashback Database can be used on both the production and
standby database to easily revert the databases to a point in time
before the user made the error.
The following steps will switch a standby
database to snapshot mode:
alter database convert to snapshot
standby;
Logs are still sent to standby but they are not
applied. The DBA can now make changes and perform testing on
the standby database.
% Keep in mind that there will be
zero data loss due to the logs still being received BUT
since they are not being applied users will not have Real Time
Query while in Snapshot Standby mode.
Once the testing is completed the DBA can revert
the database back to a physical standby database to catch-up to
production:
alter database convert to snapshot
standby;
It has now come full circle as it's a standby
database again with all changes backed out and the redo is applied
from the main database.
Creation of Standby Database
As mentioned in Chapter 4, Enterprise Manager is
now able to create a standby database from existing RMAN backups.
To access the Clone Database interface click the Data Movement tab,
then click Clone Database. Figure 9.1 illustrates this
improved interface for database cloning. Here the DBA can
create a standby database from an existing RMAN backup.
RMAN can create a standby database by copying
the files currently in use by the primary database without needing a
backup. RMAN uses the DUPLICATE command to create the standby
database.
Figure 9.3 below shows the executions steps
taken by OEM to create the standby database.
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