The following scenarios are examples of situations that benefit from using multiple
Simultaneous loading of multiple warehouse targets - Multiple warehouse targets can be loaded with a single input data source by using
multiple APPLY, and the loading of each target can be done in a parallel, scalable
manner by using multiple operator instances. The benefit of this method is that if
a failure occurs, all load operations terminate, then restart in an orderly, coordinated
The use of multiple APPLY and multiple operator instances allows input data to be
read and processed once, which minimizes I/O and system resource usage. Besides homogeneous
loading, multiple kinds of consumer operators can also be used simultaneously. For
example, warehouse A can be loaded using the Update operator while warehouse B is
loaded using the Stream operator, and so on.
This method also allows the use of the CASE DML expression in each APPLY clause so
data that is applied to each of the targets can be handled by different CASE DML expressions.
Simultaneous loading and archiving (Intermediate file logging) - Maintaining archives that accurately reflect loaded data can be problematic when
data is transformed between source and target, with only the transformed data being
written to the target. Redundant extractions and redundant transformations are time-consuming
and difficult. With the ability of Teradata PT to load multiple data targets, transformed
data can simply be loaded into both the primary target and an archive in a single
job step. For details, see “Intermediate File Logging” on page 222.