A DFSORT program phase is a large DFSORT component designed to perform a specific task such as writing the output file. An EFS program is called at various points during run-time of DFSORT program phases in performing the variety of tasks capable with an EFS program. When the termination phase is completed, DFSORT returns control to the operating system or invoking program.

EFS processing can be invoked during the initialization, input, and termination phases of DFSORT. DFSORT always calls the EFS program during the initialization phase.

During the input phase, DFSORT reads input records, and performs any INCLUDE or OMIT statement logic on the records. If the EFS program generates exit routines (EFS01 and EFS02), DFSORT calls them during the input phase.

During the termination phase, DFSORT closes data sets, releases storage, and returns control to the calling program or system. DFSORT always calls the EFS program from the termination phase.