ORA-01102: cannot mount database in EXCLUSIVE mode

I got this error when I unknowingly started a database twice with different SID'S

SQL> alter database mount;

alter database mount

*

ORA-01102: cannot mount database in EXCLUSIVE mode

ERROR at line 1:

Here is how I resolved it:

- Shutdown 

SQL> shu immediate;

ORA-01507: database not mounted

– Find out all the processes belonging to the database still running

SOLUTION:

[oracle@EDP1R3P0-pc00sby1 dbs]$ ps -ef |grep smon

– Kill all the processes

[oracle@EDP1R3P0-pc00sby1 dbs]$ kill -9 32231

– Check that there are no more processes running

[oracle@EDP1R3P0-pc00sby1 dbs]$ ps -ef |grep ora_|grep PROD

– startup the database – succeeeds

SQL> startup

ORACLE instance started.

Total System Global Area  439406592 bytes

Fixed Size                  1337072 bytes

Database Buffers           83886080 bytes

Variable Size             348129552 bytes

Redo Buffers                6053888 bytes

Database opened.

Database mounted.