ASM Unable to Recognize New Devices if Existing Disk Search String does not include them ORA-15014

ERROR :

ASM Unable to Recognize New Devices if Existing Disk Search String does not include them ORA-15014

CAUSE :

ASM discovery string was set to only '/dev/hdb*'

SOLUTION :

Add new disk discovery string in path

alter system set asm_diskstring=’/dev/hdb*’,'/dev/hdc*’
Adding new device will work now.