Oracle Message ORA-15121 - ASM file name string contains an invalid diskgroup name

ERRORASM file name string contains an invalid diskgroup name
CAUSEA file name was specified that did not contain a valid diskgroup name. The diskgroup name follows immediately after the ASM prefix character. It must start with an alphabetic character, and consist of up to 30 characters which are alphabetic, numeric, or the characters $ and _.
ACTIONCorrect the file name specification.