Why it is Called "FAST" Load

FastLoad is known for its lightning-like speed in loading vast amounts of data from flat files from a host into empty tables in Teradata. Part of this speed is achieved because it does not use the

Transient Journal. You will see some more of the reasons enumerated below. But, regardless of the reasons that it is fast, know that FastLoad was developed to load millions of rows into a table.

The way FastLoad works can be illustrated by home construction, of all things! Let's look at three scenarios from the construction industry to provide an amazing picture of how the data gets loaded.

Scenario One: Builders prefer to start with an empty lot and construct a house on it, from the

foundation right on up to the roof. There is no pre-existing construction, just a smooth, graded lot. The fewer barriers there are to deal with, the quicker the new construction can progress. Building custom or spec houses this way is the fastest way to build them. Similarly, FastLoad likes to start with an empty table, like an empty lot, and then populate it with rows of data from another source. Because the target table is empty, this method is typically the fastest way to load data. Fast Load will never attempt to insert rows into a table that already holds data.

Scenario Two: The second scenario in this analogy is when someone buys the perfect piece of

land on which to build a home, but the lot already has a house on it. In this case, the person may determine that it is quicker and more advantageous just to demolish the old house and start fresh from the ground up — allowing for brand new construction. FastLoad also likes this approach to loading data. It can just 1) drop the existing table, which deletes the rows, 2) replace its structure,and then 3) populate it with the latest and greatest data. When dealing with huge volumes of new rows, this process will run much quicker than using MultiLoad to populate the existing table. Another option is to DELETE all the data rows from a populated target table and reload it. This requires less updating of the Data Dictionary than dropping and recreating a table. In either case, the result is a perfectly empty target table that FastLoad requires!

Scenario Three: Sometimes, a customer has a good house already but wants to remodel a portion of it or to add an additional room. This kind of work takes more time than the work described in Scenario One. Such work requires some tearing out of existing construction in order to build the new section. Besides, the builder never knows what he will encounter beneath the surface of the existing home. So you can easily see that remodeling or additions can take more time than new construction. In the same way, existing tables with data may need to be updated by adding new rows of data. To load populated tables quickly with large amounts of data while maintaining the data currently held in those tables, you would choose MultiLoad instead of FastLoad. MultiLoad is designed for this task but, like renovating or adding onto an existing house, it may take more time.