The keyword PAD specifies a pad character that is used to extend the shorter of two key fields. Up to 10 sort ranges can be speci- fied. The default is to merge ascending on the complete record. Specify padding after the ordering to treat a field differently than other fields.
Output is written only to the primary output stream.
In this sense it does not delay the record, but it clearly allows a record from one input stream to overtake the record on another one. It verifies that the only connected output stream is the primary one and then commits to 0.