You asked a similar question at the start of the year suprisingly & Martins post covered it:

https://www-secure.symantec.com/connect/forums/the...

There is nothing special about multiple copies - they are simply that, another copy of the 'same' data.

One of the copies is the 'Primary' copy - all this means is that this is the coy NBU will try and use if you run a restore.

That is it, just because a copy is , or is not, primary doesn't change anything ...

and also Mariannes:

https://www-secure.symantec.com/connect/forums/the...

I don't understand why we have to say the same thing over and over.

You had the following:

Copy1      PRIMARY
Copy2
Copy3

Because Copy1 was written first, it was made the PRIMARY by default.

Then you turned Copy2 to primary:

Copy1     
Copy2    PRIMARY
Copy3

 

See? NOTHING 'happened'  to Copy1. It is still there.
Copy2 also remained Copy2. It just has the PRIMARY 'flag'.
 

If you make Copy3 the PRIMARY, you will have the following:

Copy1     
Copy2   
Copy3   PRIMARY

As I've said before - You can make Copy1 primary again or specify '-copy 1' if you want to restore from command line.