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

["David M. Malon" <malon@anl.gov>]

>  
>  This is what I understood of the usage of ROOT for MDC2:
>  
>  * Storage Manager will not be affected.
>  * ROOT will contain some event components.
>  * SM will provide Objy OID's and FID's and it's up to codes to find out
>  what files to look for the events in. I.e., the codes will do the FID to
>  ROOT file name mapping.
>  * Objy's catalog for mapping of FID to filename will be used for ROOT 
>  files too.
>  
>  Comments?
>  _________________________________________
>  Henrik Nordberg       <hnordberg@lbl.gov>
>  Scientific Data Management Research Group
>  Lawrence Berkeley National Laboratory
>  

   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