Re: To DM or not to DM...that is the question?

The Jonathan Lewis (simplified) theory of Data Warehouse and Data Marts -

        There's no such thing.

There are only rather large databases which are physically rigged to handle queries that need to thrash through large volumes of data as effectively as possible. Anything goes structurally so long as it works in the situation
you have to face.

The Jonathan Lewis (simplified) theory of Multi-dimensional databases

        There's no such thing.

A location in N-dimensional space is accessed via an N-tuple. An N+M column table (in any relational system) is the physical representation of an N+M-tuple.

An N+M column table may therefore be considered the physical representation of an N-dimensional space where every point specified has M interesting facts.

'Multi-dimensional database' is a marketing term for a table with N co-ordinate columns and M fact columns. You can model this very effectively with Oracle 8i (amongst others) with a single table and N bitmapped indices.

A more serious answer to your question -

It is certainly the case the TNF is not a good structure for the sort of data trawling you have in mind. Protoype a simple non-updatable data extract process that simplifies an interesting bit of the database into a small number of simple tables. Call this a data-mart to satisfy anyone who feels the need for a buzz-word. Find out if people use this datamart, and work upwards from there, with the assumption that you might want to redesign the code every few months.

When it really big, call it a data-warehouse; at this point you may understand the data and usage sufficiently to produce a fast-refresh, and historical trail extract. rather than a complete refresh extract.

--

Jonathan Lewis
Yet another Oracle-related web site: http://www.jlcomp.demon.co.uk

Vikas Agnihotri wrote in message <7pjq8j$s1a$1_at_nnrp1.deja.com>...
>
>My company (division, really) is just embarking on its "data warehouse"
>project. We have a rather complex OLTP system spanning the globe using
>Oracle, DCE, workflow management and a host of other
>sophisticated technologies. It automates most of the business processes
>involved in the transaction, flag errors, print customer correspondence,
>interface with the General Ledger, Accounting systems, etc. Very
>complicated.
>
>
>Is DM the right approach here? If not, how do we glean information from
>the monstrous OLTP system? Just saying "Use the right tools" is too
>naive.
>
Received on Fri Aug 20 1999 - 10:27:04 CDT