Oracle Error ORA-15251: only restricted mount is allowed in the ASM instance

Oracle Error Message

ORA-15251: only restricted mount is allowed in the ASM instance

Reason for the Error

The ASM instance was started in restricted mode, and an attempt was made to mount a diskgroup in non-restricted mode.

Solution

Start the ASM instance in non-restricted mode and mount the diskgroup again, or mount the diskgroup in restricted mode.