QSAM parallel input processing can be used to process two or more input data sets concurrently, such as sorting or merging several data sets at the same time. QSAM parallel input processing eliminates the need for issuing a separate GET macro to each DCB processed. The GET routine for parallel input processing selects a DCB with a ready record, then transfers control to the normal GET routine. If there is no DCB with a ready record, the GET routine issues a multiple WAIT macro.

Parallel input processing provides a logical input record from a queue of data sets with equal priority. The function supports QSAM with input processing, simple buffering, locate or move mode, and fixed-, variable-, or undefined-length records. Spanned records, track-overflow records, dummy data sets, and SYSIN data sets are not supported.

Parallel input processing can be interrupted at any time to retrieve records from a specific data set, or to issue control instructions to a specific data set. When the retrieval process has been completed, parallel input processing can be resumed.

Data sets can be added to or deleted from the data set queue at any time. You should note, however, that, as each data set reaches an end-of-data condition, the data set must be removed from the queue with the CLOSE macro before a subsequent GET macro is issued for the queue. Otherwise, the task could be ended abnormally.