Following the OPEN macro, tests are made to determine whether the DCBs were opened for parallel processing. If not, the sequential processing routine is given control.

In Figure 1 when one or more data sets are opened for parallel processing, the GET routine retrieves a record, saves the pointer in register 10, processes the record, and writes it to DATASET4. This process continues until an end-of-data condition is detected on one of the input data sets. The end-of-data routine locates the completed input data set and removes it from the queue with the CLOSE macro. A test is then made to determine whether any data sets remain on the queue. Processing continues in this manner until the queue is empty.