Friday, November 1, 2013
There is always a starting point (E) and an end point (L) to the transformation (T), this time I would like to share some of my experience concerning the ETL process.
This will no be so much about how to do this or that, but more about the delicate and sometime awkward situations that can arise in the process.
If you are doing custom transformation work or it is just part of your daily work, the hardest part of the ETL process can sometimes be the process around the technicality of it.
Since you are responsible for the 'black box' for most people (and managers especially) you are bound to get the blame if it goes wrong.
Lesson 1: make it clear from the start what your responsibilities are!
Make sure that the parameters and expected results of your job are well defined before you even open FME!
This can take some time and you will be seen as a pain in the .... but it can save you a lot of pain and it will make your goals clear and well defined.
In most cases involving large and complicated database schema and design, you are dependent on others to provide you an insight about the database schema or even better: queries to preform on the database.
Most of the times you get a reaction like: " I thought you are the ETL specialist...." or " Don't you know how to do it yourself?", sounds familiar?
Lesson 2: clearly define the input and expected results (especially if large and complicated database schema is involved)
OK you got over the first hurdles and created your workspace and it works or at least you think it does, but wait a minute after some time it turns out that it is not providing the expected results (oops embarrassing moment) but hey we are all human and we make mistakes.
So you rack your brain trying to find where the mistake is done. Eventually you find no fault in your work and the workspace does what it is suppose to do.
In fact you have delivered what was possible based on the information you got, the problem arises when you are not supplied the correct information.
Lesson 3: document the defined input, expected results, responsibilities and ETL process.
Despite it all it can always go bad, there is always a rotten apple.....somewhere in between it all.