karthick srini wrote:

> Dear Team (I mean the members who are subscribed to
> the forum),
>
> I do understand that we cannot create FK when there
> two connections. I am new to firebird. I am in the
> process of learning firebird design/architecture. In
> that process, I am just trying out to figure out the
> reason which restricts meta data update , so what I
> can follow a better alternative solution when I use
> firebird in my application.

The bottom line is that changes to the structure of the database can
result in complex problems especially when adding foreign keys, triggers
and other automatic relations. MySQL has never had to deal with these
problems - until now - and they are now seeing the problems that
Interbase designed out many years ago. Attempts by Borland to add some
more 'flexibility' have resulted in the mess that Firebird is currently
trying to unravel with FB2/Vulcan.

One rule that I have enforced for many years is not to make metadata
changes to running systems. None of my system updates have suffered from
the problems seen at some sites where complex changes have been added in
real time without a 'get out clause' and resulted in systems being down
for days. Just because you CAN do something does not mean it is right,
but until one has tested a new structure, old data should stay in the
old format ;) I'm currently working on an update that will take a couple
of hours to dump the data across, but that is much safer and not much
longer than converting the existing database - in real time. The first
attempt at a dump through up several errors that would have crashed a
simple 'change the metadata' ;) It's amazing what people can add as data
even with complex checks to prevent errors :)

--
Lester Caine
-----------------------------
L.S.Caine Electronic Services