Re: Is modifying content in 'Data mart' possible for the applications quering it?

From: guser78 <>
Date: Wed, 17 Mar 2010 03:16:46 -0700 (PDT)
Message-ID: <>

On Mar 14, 3:16 am, Mark D Powell <> wrote:
> On Mar 12, 10:01 am, Shakespeare <> wrote:
> > Op 12-3-2010 14:34, guser78 schreef:
> > > I would like to know whether the content of the 'Data mart' tables be
> > > modified by the Marketing applications.
> > > I understand that the 'Data mart' is filled by the ETL layer by
> > > extracting and transforming the data from the Data warehouse(for
> > > 'Dependent datamart' case).
> > > After it is filled, does the Marketing application have the option of
> > > only 'read'/'query'ing the data from the 'Data mart'? In our usecase,
> > > there is a specific case where the applications need to write some
> > > minor data occasionally into the Data mart (into the existing tables,
> > > not in any new tables). Is that Technically feasible with the 'Oracle
> > > Data mart'?
> > Sure, why not? As long as you realize that all changes may be lost when
> > a new ETL process has run.
> > Shakespeare
> I think part of the answer here might depend on exactly what kind of
> updates are bieing talked about. As I understand it a 'real' datamrat
> is an extraction of a subset of data from a data warehouse for a
> specialized use.  You would normally expect a datamart to be
> completely refreshed from a source data warehouse every N periods of
> time in which case your changes would be lost.  However, it is normal
> to process the datamart data to perform summaries, aggregations, and
> produce specialized reports.  Such processing would need to be redone
> with every refresh of the data anyway and is hopefully not what the OP
> is asking about.
> If the customer wants to apply real changes to the data that does not
> fall into what would be considered normal datamart processing then
> either the changes would need to be propogated back to the source
> warehouse or a means would need to exist to allow reapplication of the
> changes after every refresh.  If you are in this situation then the
> possibility exists the customer does not properly understand the
> datamart concpet, the warehouse is lacking necessary information and
> it should really be added there, or the datamart has been butchered
> into being another data warehouse.  This last can happen due to
> company polotics and/or a lack of a lack of knowledge on the part of
> the developers on the total system data flow: source to warehouse to
> datamart that should be in effect.
> What I am suggesting is if you are unsure of applying changes to the
> datamark you may want to review the data in the datamark itself, check
> into the source feeds, undate frequencey, and ask about the history of
> the datamart so that you can put the changes into perspective.  Then
> you can determine how feasible the requested changes are and if the
> changes really need to be in the source warehouse or even earlier in
> the data creation stream.

Excellent! I can't expect a better reply than this. Thanks!

So, now I understand that I will have to change the ETL layer to the 'Data mart' dynamically.

Majority of the requests will be 'read' requests and can be fulfilled by reading the data attributes from the Data mart. The Admin 'write' requests which can come during run time, should be able to adapt the ETL layer (layer between 'Data warehouse' and 'Data mart'). I guess, we need to write an additional software module (for e.g. JDBC) to interpret 'Admin write' requests and adapt the ETL layer accordingly.

Does that sound a reasonable approach? Received on Wed Mar 17 2010 - 05:16:46 CDT

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