How to Prevent ASM Diskgroup Automatic Mount

1) To disable certain ASM Diskgroup automatic mount on all RAC nodes, run below command as grid user:

$ srvctl disable diskgroup -diskgroup testdg

2) To disable certain ASM Diskgroup automatic mount on specific RAC node, run below command as grid user:

$ srvctl disable diskgroup -diskgroup testdg -node racnode1

3) To check the status of ASM diskgroup:

$ srvctl status diskgroup -diskgroup testdg -detail -verbose
Disk Group testdg is running on racnode1, racnode2
Disk Group testdg is disabled

Note: You cannot run the “srvctl start” command on a disabled object until you first re-enable the object