ORA-01102: cannot mount database in EXCLUSIVE mode

Error happened when try open database :

SQL> startup
ORACLE instance started.

Total System Global Area 267227136 bytes
Fixed Size 2212496 bytes
Variable Size 205524336 bytes
Database Buffers 54525952 bytes
Redo Buffers 4964352 bytes
ORA-01102: cannot mount database in EXCLUSIVE mode


 In alert.log
sculkget: lock held by PID: 12359
ORA-09968: unable to lock file
Linux-x86_64 Error: 11: Resource temporarily unavailable
Additional information: 12359
ORA-1102 signalled during: ALTER DATABASE MOUNT...
On OS level :

[oracle@localhost trace]$ ps -ef | grep pmon 

oracle 10222 1 0 10:27 ? 00:00:00 ora_pmon_ORCL
oracle 2522 1 0 Nov09 ? 00:00:06 ora_pmon_orcl
Use :

 Kill -9 10222 2522

Then
1-After that fire export ORACLE_SID= (watch case sensitive )
2-sqlplus / as sysdba
3-startup ;