What is the effect of the NOBS= option in a DATA step?

The NOBS= option in a DATA step is designed to specify the number of observations to read from a dataset. When this option is used, it allows the programmer to know the total number of observations present in a dataset. This is particularly useful when building conditional logic or loops that depend on the number of records available in the dataset. By retrieving the observation count, SAS helps manage the data manipulation efficiently.

For instance, if you are interested in processing only a specific number of records or need that information for validation purposes, NOBS= provides clarity about the dataset's size before further operations are performed. It enables you to tailor processing logic based on how many records you are dealing with, ensuring that your data transformations proceed as intended without exceeding the limits of the available data.