Data Guard creation of logical standby Tips Oracle Database Tips by Donald BurlesonDecember 9, 2015

Oracle Data Guard

Simplified creation of logical standby in 10g and beyond

In earlier releases, it was difficult to create the logical Oracle instance without shutting down the primary database. If the online backup was used to create the logical standby, a quiesce of the database at the end of backup is needed, which also required the resource manager. The SCN must also be recorded. These actions necessitated the primary database shutdown.

With Oracle Database 10g, there is no need to quiesce the primary database. The required information is read through the logical standby control file. Oracle recommends the use of a new method to create a logical Oracle instance that is explained next.

his new method will allow the DBA to achieve 'zero down time instantiation' by using an online backup of the primary database and the logical standby control file.

The suggested steps are as follows:

1. Take an online backup of the primary database. Optionally, the offline backup of the primary database can be used.  If the offline backup is used, all the archive log files from the time of the backup are needed.
    

2. After the backup is obtained, create a logical standby control file with the newly provided CREATE LOGICAL CONTROL FILE command. For example, use the following statement:

ALTER DATABASE CREATE LOGICAL STANDBY CONTROL FILE AS 'mylogicalstandby.ctl';

The logical standby control file is similar to the physical control file but has additional information.

3. Copy all the backup files, archive files, and logical standby control files to the standby host.
    

4. After restoring all the files, mount the Oracle instance with the logical standby control file.
    

5. Set up the log transport services on the primary.
    

6. Start the managed recovery on the standby database. Execute the following statement.

ALTER DATABASE RECOVER MANAGED STANDBY DATABASE;

7. Then, begin applying the redo logs. To start the log apply services, execute the statement:

ALTER DATABASE START LOGICAL STANDBY APPLY;