Archives of the TeradataForum
Message Posted: Mon, 04 Nov 2013 @ 15:36:27 GMT
Update to SCD Type II:
Please note that there are actually six (6) Classes of SCD, not just Type I & II. The term "Type II" is utilized by the various vendors, because they do not have techniques to address all the other Classes and using that term allows them to "hide behind" the fact that they do not have solutions to Classes 3-6. Class 1 does not need to addressed, as it is the old, plain, overwrite the records and discarding of history in the process. There is a "Class 2" SCD, but that is what many would call an "audit trail", although that is not technically 100% accurate for the purists. The current implementation of SCD by TD is in Type II format, aka Class 3 SCD.
So for the record, Type II is an SCD misnomer, and is in actuality "Class 3" SCD, aka to be more technically accurate. I write all this because using Type I & II, interferes with and prevents technically accurate and precise discussions of the state of SCD data in various shops; not only TD, but also Oracle and SQL Server, etc. The SCD classes of 2, 4, 5 and 6 are omitted from the SCD discussions, whereas they should be included to perform valid analysis of SCD's in a shop.
Please note that our shop also saves data in an SCD "Class 5" storage format; no vendor has ever proposed a solution or process to save data in a Class 5 (or 6) manner. As far as I know, we are the only TD shop that saves in Class 5 SCD format/protocol.
So I have now placed in the record the fallacy and gaps represented by Type 1 & Type II SCD. The more appropriate scope for SCD discussion should be to use the Classes of 1-6, with Class 3 replacing "Type II", in discussions.
This is especially important, because many shops contain SCD Class 2 stored data (not to be confused with Type II, which is Class 3 SCD). Class 2 SCD formatted data is massive storage "hog", i.e. very inefficient, which should be converted to Class 3 SCD (ok, Type II, ugh).
|Copyright 2016 - All Rights Reserved|
|Last Modified: 24 Jul 2020|