Oracle internals, debugging and undocumented features
From note :
Note: On release 11g and onwards you can use the ASMCMD to backup the ASM metadata.
From Oracle documentation itself:
Syntax and Description
location_of_backup is the location in which you want to store the backup file
dgname is the name of the disk group that you want to back up
ASMCMD [+] > md_backup -b /tmp/backupdg -g md_data -g md_logs
Disk group to be backed up: MD_LOGS
When open backupd file there are only entries for this disk groups.
It will generate report only on last group!! Not a big deal but ASM is full of bugs..