Am I right in thinking that I could create a server application which
accesses a single catalog, and which can then have multiple databases
accessed by threads of the server. Each database would have the same
tables (and thus table names) but obviously with different data.

This is all do-able yes?

Can a single application access multiple catalogs?

Just pondering...

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Matthew Jones

Matthew

>Am I right in thinking that I could create a server application which
>accesses a single catalog, and which can then have multiple databases
>accessed by threads of the server. Each database would have the same
>tables (and thus table names) but obviously with different data.
>
>This is all do-able yes?
>
>Can a single application access multiple catalogs?

Shouldn't be any problem. Its the config that has to be unique not the catalog. If you use memory tables you're doing exactly what you want already.

Roy Lambert

Matthew,

> Am I right in thinking that I could create a server application which
> accesses a single catalog, and which can then have multiple databases
> accessed by threads of the server. Each database would have the same
> tables (and thus table names) but obviously with different data.
>
> This is all do-able yes?

I don't think so. The catalog is the "description" of a database with
all its tables, procedure etc.

http://www.elevatesoft.com/manual?action=viewtopic&id=edb2sql&topic=architecture

What you want, are different databases with identical table structures.

Uli

Matthew,

after having read Roy's answer, I am not sure, if I probably
misunderstood your question.

Uli

Uli Becker wrote:

> after having read Roy's answer, I am not sure, if I probably
> misunderstood your question.

Thanks - I think you answered the part of multiple catalogs, and that
does seem like a stretch.

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Matthew Jones

Roy Lambert wrote:

> Shouldn't be any problem. Its the config that has to be unique not
> the catalog. If you use memory tables you're doing exactly what you
> want already.

I shall have to have a play...

--

Matthew Jones

Matthew


>Thanks - I think you answered the part of multiple catalogs, and that
>does seem like a stretch.

I think I see where I misunderstood your question. I didn't understand that you wanted a single catalog controlling lots of different databases. That is not possible.

Just to make it clear I am using the term database to mean an alias to the directory a collection of tables is in.

The diagram Uli pointed to should really show multiple databases each with their own catalog beneath the configuration.

What you could  possibly do (ie I haven't tried it) is set each database to use an in-memory catalog and then write that each time the app is opened. However, I think that will give other problems.

Its still not that bad. Its easy enough to create the first database with its catalog and then clone that as and when needed.

Going back to the old DBISAM days. There the tables carried their own metadata so creating a new database sort of felt like you were just copying the tables now you have to create the catalog which is pretty much the same just that tables aren't created until needed.

Its also a lot easier to replicate all of the structure, functions, procedures etc, especially now Tim has the CreateSQL column.

Roy Lambert

Roy Lambert wrote:

> Matthew
>
>
> > Thanks - I think you answered the part of multiple catalogs, and
> > that does seem like a stretch.
>
> I think I see where I misunderstood your question. I didn't
> understand that you wanted a single catalog controlling lots of
> different databases. That is not possible.

I think it is possible, I've just done it in EDB!

Basically, you have one catalog (the Session control file) but that can
have multiple databases, each in different locations on disk. Thus I
have in my EDB session the web store database, and another I just
created. I can, apparently, create more, but I am pondering keeping a
single database for multiple "data sets" for a server. Not sure yet,
but it is happy enough to work.

--

Matthew Jones

Matthew

>Basically, you have one catalog (the Session control file) but that can
>have multiple databases, each in different locations on disk. Thus I
>have in my EDB session the web store database, and another I just
>created. I can, apparently, create more, but I am pondering keeping a
>single database for multiple "data sets" for a server. Not sure yet,
>but it is happy enough to work.

Slaps Matthew around the head - "get your jargon right boy!" he shouts.

The session has a configuration file (EDBConfig.EDBCfg) not a catalog. The database has the catalog ((EDBDatabase.EDBCat)

I'm being a bit pedantic here but its important.

Databases can talk to each other via SQL as long as they share a session. Out side of session boundaries you'll have to use navigational methods.

Roy Lambert

Roy Lambert wrote:

> Slaps Matthew around the head - "get your jargon right boy!" he
> shouts.
>
> The session has a configuration file (EDBConfig.EDBCfg) not a
> catalog. The database has the catalog ((EDBDatabase.EDBCat)
>
> I'm being a bit pedantic here but its important.

Thanks. Catalogs were something I learned about in something like a
crappy BBC Micro application, and I didn't like it much then. (The
Atari 800 was a much more capable computer, but try telling that to a
BBC Micro fan... 8-)


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Matthew Jones