Subject Re: [IB-Architect] Backward compatability with previous versions of gdb files
Author Jim Starkey
At 09:55 AM 5/1/00 +1000, Helen Borrie wrote:
>I heartily agree with the argument for not having a client tool that
>upgrades the ODS of the live database. That would be very scary.

The philosphy in DEC's DBMS-11 and VAX DBMS products was just
that -- write a one-time utility to upgrade a database in place.
And when it didn't work -- and there was always an unanticipated
problem -- the customer was left with a database of Jello.

This was one of the two major motivations for the Y-valve architecture
that DEC, Interbase, and now Oracle are enjoying. In the DEC
world, it meant that two completely different database systems,
Rdb/VMS and Rdb/ELN could co-exist on the same system, moving
databases back and forth with a simple backup and restore. One
of the early pieces of Interbase was a VMS image that mimiced
DEC's Y-Valve that through the magic of logical names could
splice in Interbase. One of my early joys at Interbase (then
Groton Database Systems) was readying an Interbase database running
on an Apollo from VAX Datatrieve. Similarly, QLI was completely
capable of accessing an Rdb/VMS system.

Good architecture means eliminating individual attention to
each of the cross product of the feature set. If you look
at software like Legos with clean, interlocking interfaces
you can build much larger, more robust products than if you
you view software as Play-Doh.

Jim Starkey