Changing the size and number of the online redo logs is sometimes done to tune the database. You can add redo log file groups or members to the primary database without affecting the standby database. Similarly, you can drop log file groups or members from the primary database without affecting your standby database. However, these changes do affect the performance of the standby database after switchover.

For example, if the primary database has 10 redo logs and the standby database has 2, and then you switch over to the standby database so that it functions as the new primary database, the new primary database is forced to archive more frequently than the original primary database.

Consequently, when you add or drop an online redo log at the primary site, it is important that you synchronize the changes in the standby database by following these steps:

1. If managed recovery is on, you must cancel it before you can change the logs.
2. If the STANDBY_FILE_MANAGEMENT initialization parameter is set to AUTO, change the value to MANUAL.
3. Add or drop an online redo log:
   • To add an online redo log, use a SQL statement such as this:

     SQL> ALTER DATABASE ADD STANDBY LOGFILE 'prmy3.log' SIZE 100K;
     
     

   • To drop an online redo log, use a SQL statement such as this:

     SQL> ALTER DATABASE DROP STANDBY LOGFILE 'prmy3.log';
     
     

4. Repeat the statement you used in step 3 on each standby database.
5. Restore the STANDBY_FILE_MANAGEMENT initialization parameter and the managed recovery options to their original states.