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A Data Stage contains instructions to read the raw data and generate an Intermediate Data File (.IDF) from them. The raw data normally consist either of punch card images or ASCII (character) data, but can also be entered from the keyboard. The .IDF file contains variables defined by your instructions, and generated from the raw data.

Additionally, in Data Stages, it is possible to:

validate the data, producing a report of errors or correcting the data online

produce hole counts (marginals)

output cleaned or recoded data files

produce a small number of tables

If you require more than a few tables it is more efficient to put these in a separate tables stage. Tables for weighting (rim/targets) may be placed in the Data Stage to avoid an extra pass over the data.