ORA-15097: cannot SHUTDOWN ASM instance with connected client

I was trying to shutdown one of our ASM Instance but failed to do so because of error "ORA-15097: cannot SHUTDOWN ASM instance with connected client".

There are certain active processes accessing and are active on ASM Instance. To shutdown the ASM instance you need to perform either shutdown abort option or kill all the active processes on ASM Instance.

Try to find out the active process using ps -ef command.

bash-3.00$ sqlplus

SQL*Plus: Release 11.2.0.2.0 Production on Tue Jun 14 08:18:17 2011

Copyright (c) 1982, 2010, Oracle.  All rights reserved.

Enter user-name: /as sysasm

Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
With the Automatic Storage Management option

SQL> shut immediate
ORA-15097: cannot SHUTDOWN ASM instance with connected client (process 15628)
SQL> exit
Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
With the Automatic Storage Management option
bash-3.00$ kill -9 15628
bash-3.00$ sqlplus / as sysasm

SQL*Plus: Release 11.2.0.2.0 Production on Tue Jun 14 08:18:48 2011

Copyright (c) 1982, 2010, Oracle.  All rights reserved.


Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
With the Automatic Storage Management option

SQL> shut immediate
ASM diskgroups dismounted
ASM instance shutdown
SQL>