I already did but it did not work. So I tried

SQL> alter database mount;
alter database mount
*
ERROR at line 1:
ORA-00205: error in identifying controlfile, check alert log for more info

I checked the controfile and got this

Mon May 7 11:12:43 2001
ORA-00202: controlfile: '/u09/ora09/POLICY/ctrlPOLICY01.ctl'
ORA-27086: skgfglk: unable to lock file - already in use