Help needed for history migration

[vaass]

Hi all
i am in process of migrating history into the existing data warehouse. Actually i have the current data warehouse with data from March'04. I have to populate data for 2 yrs back from March'04. Some of the kpi's are dependent on the previous months numbers. Actually our plan is to build from the beginning of Apr'02, the time which is going to take to complete this build will be around 3-4 months. The business is thinking that we have to wait till that time to see the figures. The expectation of the business is that they want us to build the history in the reverse order i.e starting from Feb'04 and going back till Apr'02, if we follow this way, we will be ending up in building wrong figures since we do not have the previous month's data. Is there anyway to overcome this...have anybody experienced this kind of situation. Pls guide me with some suggestions

Thanks a lot
Vasudevan S

 

[johnherman]

You have identified your problem, can't calculate running numbers or numbers dependent on previous numbers without doing the earliest history first. If space permits, create a copy of the current DW and load history into the copy. When you are ready (balancing, validation, QC/QA) then either change the pointers to the new database, or back it up and overwrite the current production database (back up current production before overwriting, of course).

The alternative is to build backwards, but do not populate the columns which have dependencies until the end. Better to have no data for a column than wrong data.

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The trouble with doing something right the first time is that noboby appreciates how difficult it was.
- Steven Wright