What does the KEEP statement do in a DATA step?

The KEEP statement is used in a DATA step to specify which variables should be retained in the output data set. When you include a KEEP statement, only the variables listed within it will be included in the final output, while all other variables that are not mentioned will be omitted. This is particularly useful when working with large datasets or when you want to focus on a subset of variables for analysis and reporting.

Using the KEEP statement helps in reducing the size of the output dataset by eliminating unnecessary variables, which can enhance performance or clarity in subsequent analysis steps. This functionality aligns with how variable management is handled in SAS programming, allowing for efficient data manipulation.