Re: Objy/ROOT discussion at today's phone meeting

[Arie Shoshani <arie@math.lbl.gov>]

>    This is my understanding as well, with the clarification that the SM 
>    will ALSO be a client of the FID-to-filename mapping, so that the 
>    Cache Manager can deliver the correct files by the time the user code 
>    tries to reach them.  
> 
>    I am not yet comfortable with the proposed approach to generating 
>    FIDs for ROOT files, but Henrik's text does correctly describe the 
>    current proposal.  I have no objection to having Objectivity manage 
>    the FID-to-name mapping; it's the consumption of Objectivity DB ids 
>    (there are only 64K of them available--scalability implications?) and 
>    faking Objectivity into believing that ROOT files are federation databases 
>    (implications for database administration operations (install, 
>    attach/detach, copy, ...?) that still bother me.  (Some Objectivity tools 
>    check whether an alleged database file is really an Objectivity database.)
>    There are certainly other ways to generate unique FIDs between ROOT and 
>    Objectivity, as well as other ways to let Objectivity manage the mapping.  
> 
>    I realize that the proposed approach will probably be okay for MDC2.  
>    Scalability, though, is the GCA's raison d'etre, so I am reluctant to 
>    deceive Objectivity in a way that may diminish scalability unless there 
>    is a good reason for it.  
> 
>    Can anyone allay my concerns?  Does anyone else share them?
> 
>    Cheers,
> 
>    David

I think the limitation of the 64K files is the problem here whether or not you
assign some of the file ids to ROOT files.  So, the naswer to your concerns is 
that the Objectivity people plan to have Files at the container level which 
makes the total of about 4 billion files, so we should be OK then.

Arie.