PROBLEM:

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

SQL> startup mount;
ORACLE instance started.

Total System Global Area 1.4663E+10 bytes
Fixed Size                 15697000 bytes
Variable Size            9865010072 bytes
Database Buffers         4731174912 bytes
Redo Buffers               51404800 bytes
Database mounted.
SQL> select name from v$database;

NAME
---------
TESTDB

SQL> drop database;
drop database
*
ERROR at line 1:
ORA-12719: operation requires database is in RESTRICTED mode

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

startup mount exclusive restrict
drop database;

Another way to drop database is:

startup mount
alter system enable restricted session;
drop database