ORA-15260: permission denied on ASM disk group

Problem:

$ sqlplus / as sysdba

> alter diskgroup ocrdg add site sitec quorum failgroup fg3 disk '/dev/oracleasm/OCR01_3' name OCR01_3 size 10240M rebalance wait;
alter diskgroup ocrdg add site sitec quorum failgroup fg3 disk '/dev/oracleasm/OCR01_3' name OCR01_3 size 10240M rebalance wait
*
ERROR at line 1:
ORA-15032: not all alterations performed
ORA-15260: permission denied on ASM disk group

Soultion: login as sysasm

$ sqlplus / as sysasm

> alter diskgroup ocrdg add site sitec quorum failgroup fg3 disk '/dev/oracleasm/OCR01_3' name OCR01_3 size 10240M rebalance wait;