Head stage
The Head Stage selects the first N rows from each partition of an input data set and copies the selected rows to an output data set. You can sample data using this stage.
The Head Stage is a development and debug stage. It can have a single input link and a single output link. It is one of a number of stages that IBM® DataStage® provides to help you sample data, see also:
- Tail stage, Tail stage.
- Sample stage, Sample stage.
- Peek stage, Peek stage.
The Head Stage selects the first N rows from each partition of an input data set and copies the selected rows to an output data set. You determine which rows are copied by setting properties which allow you to specify:
- The number of rows to copy
- The partition from which the rows are copied
- The location of the rows to copy
- The number of rows to skip before the copying operation begins
This stage is helpful in testing and debugging applications with large data sets. For example, the Partition property lets you see data from a single partition to determine if the data is being partitioned as you want it to be. The Skip property lets you access a certain portion of a data set.
When you double-click the stage, the properties panel opens. The properties panel has three tabs: