Change ASM Diskstring parametr in RAC database

ORACLE: 11.2.0.4

RAC: 2 nodes

NOTE: with existing ASM Diskstring parameter /dev/* works great. No issue.

Question: I want to change the ASM Diskstring parameter from /dev/ to /dev/mapper and it is erroring out. How would I fix this issue?

1. 1st node, I ran the alter command and got the error below:

alter system set asm_diskstring='/dev/mapper/*' sid='*'scope=both;

ERROR at line 1:

ORA-02097: parameter cannot be modified because specified value is invalid

ORA-15014: path '/dev/oracle_cx380_phxdev_fra01' is not in the discovery set

Permissions:

under /DEV = brw-rw----.  1 oracle oinstall 253,   9 Jul 26 10:55 oracle_cx380_phxdev_fra01