What is the significance of the OBS= option in a DATA step?

The OBS= option in a DATA step is used to limit the number of observations that are processed from the input dataset. When this option is specified, SAS processes only the observations from the beginning of the dataset up to the number specified in the OBS= option. This is especially useful when you want to work with a smaller subset of your data for testing or debugging purposes. By controlling the number of observations processed, users can save time and resources, particularly when dealing with large datasets.

This option does not create or rename output datasets, adjust sorting order, or define observation indices. Instead, it solely focuses on limiting the number of observations that the DATA step will consider, which can be extremely helpful in managing large datasets efficiently.