ASM disk groups are the foundation of ASM. It is where your data will be stored. ASM disk groups can be allocated to raw disk, cooked disk. To add a ASM disk group you first need to set the ASM_DISKSTRING parameter. You can then add disk groups to your ASM instance.
This is a companion discussion topic for the original entry at https://blog.toadworld.com/configuring_26_managing_asm_disks#:~:text=If%20you%20happen%20to%20change%20ASM_DISKSTRING%20dynamically%20and,will%20result%20in%20a%20failure%20of%20the%20command.