srvctl modify database syntax explanations

Hello,

I dont understand syntaxe of the bellow command :

srvctl modify database -d <db_unique_name> -a '<disk group name here without the '+'>,<disk group name here without the '+'>

Why there is just one quote after the -a ?

Why did the diskgroup name is displayed 2 times??

Is it for the <FRA disk group name here without the '+'>,<DATA disk group name here without the '+'> ?

In my case, FRA and DATA are in the same diskgroup.

From Grid USER:

ASMCMD> ls

CRSVOTE/

VINCDG/

So this command line should be:

srvctl modify database -d VincDatabase -a VINCDG,VINCDG