by steve-myers » Thu Jul 07, 2011 8:55 pm
The idea of the internal reader first appeared in the OS/300 HASP program. The idea, of course, was to provide a mechanism for a program to submit JCL for execution rather than submit a job using cards or from a dataset.
It was radically rewriiten for the first release of MVS, and rewriiten again for z/OS 1.7, though this last rewrite did not require JCL or user program changes. The MVS change required JCL changes, and it included an API that allowed user program control and the ability for a user program to retrieve information about the job it is sybmitting.