As mentioned, a physical standby database is needed to create a logical standby database. It is assumed that we have a Data Guard configuration with a primary and one or more physical standby databases, which are synchronized with the primary. In order to create a logical standby database, we should first check the primary and the physical standby databases and make them ready for a logical standby conversion. These configurations are as follows:
- Stopping the media recovery on the standby
- Configuring primary database initialization parameters to be ready for a logical standby role transition
- Building the LogMiner dictionary on the primary
- If standby is RAC, converting it to a single instance temporarily
After completing these tasks, we continue the process of converting the physical standby into a logical standby with the following tasks:
- Recovering the standby to the SCN that the LogMiner dictionary was built with
- Re-enabling RAC on the standby if it exists
- Modifying the archival initialization parameters for the standby
- Opening the database with resetlogs
- Starting SQL Apply on the standby
It's important to complete all these steps for a successful logical standby database configuration.
Tip
If Data Guard broker is used, it's advised to remove the physical standby database from the broker configuration before starting the logical standby conversion process. If you don't, broker will still show the standby database as a physical standby even if you convert it to a logical standby database and you'll struggle with this problem later on.