[Info-Ingres] Multi-database table references

[Roy Hann]

"Raghavan" <rajiraghavan at gmail.com> wrote in message 
news:1190611013.872340.6100 at 50g2000hsm.googlegroups.com...

> I have a legacy application running for more than15 yrs. Now I am
> wanting to use the concept of creating multi-databses for various
> reasons.

I don't know how well-defined the term "multidatabase" is defined, but I 
sort of think it implies a mix of products.  Something like say, some Oracle 
databases and some MS SQL Server databases and some Ingres databases all 
tied togther (possibly using Ingres/Star and suitable gateways).  Is that 
what you are intending?  Or do you want to distribute the tables of one 
existing Ingres database amongst multiple future Ingres databases (i.e. a 
single product, with a single concurrency control model)?

> The problem is,
> 1. I have to segregate the applications to various databases.
>    and assign tables pertainign to those databases.

That could be a problem sure.

> 2. In the current applciations as it is a single production database,
> i will have to introduce the concept of aliases for various tables to
> minimise the coding of the existing applications.

Ingres supports table synonyms.

> Has anyone handled such a scenario?

I am not clear what the scenario is.  Are you just breaking up one big 
database into more manageable independent pieces, or do you need to operate 
the pieces as a single federated database with distributed (2PC) 
transactions?

> Can anyone help me?

I don't know.  What is the business problem to be solved?  What is the 
business case for doing it (I.a. how much trouble can the solution be before 
it offsets the benefit)?  What mix of products?  Local databases or 
geographically distributed?   How many users?  What is the mix of on-line 
and batch processing?  What are the response-time expectations?

Whatever it is you have in hind, it sounds like it won't be trivial.  Even 
using Star to run a homogeneous federation of Ingres databases is 
problematic.  Adding Enterprise Access Gateways to the mix takes it to a 
whole new level.  I have done it when there was no choice, but I don't think 
I would ever set out to do it if I didn't absolutely have to, and the 
business case would have to be unassailable.

Roy