Oracle: prevent Active DataGuard from being used

Using a standby database is a good way to increase availability and redundancy to an Oracle database. Switching over the database to another host and/or data center also helps to decrease outages for patching.

Best practise for a database installation is to always have Grid Infrastructure (GI) installed. Sure - it needs more disk space and also patching components, but it also helps us when switching over: it starts database using the right role - either PRIMARY or PHYSICAL_STANDBY.

But there are still some Oracle installations without GI. They use some custom scripts to start the database(s), mostly from within systemd.

Stopping databases on these systems is quite easy:

# dbshut $ORACLE_HOME

dbshut goes through /etc/oratab and stopps all databases and listener(s).

Starting them is also easy:

# dbstart $ORACLE_HOME

On a primary site, this is quite ok. But on a standby site, databases are started in OPEN mode, which leads to a standby database using Active DataGuard. You can check it like this:

SQL> select OPEN_MODE from v$database;

READ ONLY WITH APPLY

But you can use an underscore parameter to prevent the standby database from being opened using Active DataGuard:

SQL> alter system set "_query_on_physical"=FALSE scope=spfile sid='*';

As it's not a dynamic parameter, you have to restart the database for this.

After starting the database using dbstart $ORACLE_HOME, the database will started going through NOMOUNT and MOUNT state. It will also try top open, but since the parameter is set, OPEN mode will prevented.