PROBLEM:

While dropping a database in mount stage got below error.(ORA-12719)

SOLUTION:

So drop a database we need to start the database in exclusive restrict mode.

oerr ora 12719
12719, 00000, “operation requires database is in RESTRICTED mode”
// *Cause: This command can only be run when the database is in RESTRICTED mode
// *Action: Ensure that the system is in RESTRICTED mode

Another way to drop database is: