Extended storage question.

[Steve Gentry]

I trying to figure out what information I'm getting when I issue the  Q  XSTORE  MAP  command.
My current   XSTORAGE is setup as follows:

q xstore                                                          
XSTORE= 4608M                                      
XSTORE= 4608M userid= SYSTEM usage= 21% retained= 0M pending= 0M  
XSTORE MDC min=0M, max=0M, usage=0%                              
XSTORE= 4608M userid=  (none)  max. attach= 4608M

I don't have any assigned to a specific user so I assume that the system (cp?) is in control
of it and is thus allocating it as it sees fit.
As shown above, 21% is in use.  But, who is using it?
I issue the  Q  XSTORE  MAP  command and get the following:

q xstore map                                            
    START       SIZE      STATUS         %-IN-USE  %-UNUSABLE
       0M              4608M       CP                        21%                    0%    

 I was hoping that it would tell me that  userX  was using so much,  userY  was using so much, etc.
Or does a user show up in the   q xstore  map  when the storage has been attached to a
specific user?  Say for instance I   attach   1000M  to a db2  machine/user.  Will that userid then
show up in the list  generated by the Q  XSTORE  MAP command?  If this is the case is there
a command that will tell me who is using  XSTORE and how much (either a percentage or a
total amount used).  
And should I let the system allocate it or should I issue the attach statement?  I can see using the
attach statement if you absolutely want a user to have a specific amount of  XSTORE because of
a constrained environment.  But what about non-constrained?
Thanks,

Steve G.