History
OS/360's job input and print queuing had limited operational flexibility and performance. This was addressed by two field-developed packages: Houston Automatic Spooling Priority (HASP), and Attached Support Processor (ASP).
HASP originally managed job scheduling and print and punch output for a single OS/360 computer, such as a single 360/65. "Multi Access Spool" capability was added for to let peer computers share a common job queue and print/punch output queues. HASP was developed by IBM Federal Systems Division contractors at the Johnson Space Center in Houston. In MVS, HASP became the standard part of system, Job Entry Subsystem 2 (JES2). It was many years before the HASP labels were removed from the JES2 source, and the messages issued by JES2 are still prefixed with $HASP.
ASP stood for Attached Support Processor, and was developed to provide efficient use of multiple OS/360 systems with a shared workload. It allowed one central system to distribute jobs to multiple connected systems. Typically, a small mainframe such as a 360/40 (the support or global system) controlled one or more 360/65 or larger processors (main or local systems). The computers were connected through selector channels on each host attached to channel to channel adapters, for an early form of short distance, point-to-point computer networking. ASP required the purchase of an additional computer to manage input and output of the hosts running the job workload, which was economically justified by the high cost of standalone byte-multiplexor channels needed to drive printers and punched card reader devices: the 360/50 and smaller systems had a built-in byte multiplexor channel, whereas the faster 360/65 and larger systems required a relatively expensive standalone unit. Using ASP made it possible to avoid the cost of the byte multiplexor channel, and offloading the job scheduling, print, and card handling also offloaded those functions from the larger machines. ASP evolved from the design of the 7094/7044 Direct Coupled System, using data channel to data channel communication. It was primarily targeted at large government agencies and defense contractors that might have as many as six 360/65s all being scheduled and managed by a separate ASP machine. An uncommon variant, Local ASP (LASP) was a single large machine with the ASP functions running on the same machine. ASP became JES3.
Source code was provided to IBM customers for both ASP and HASP, and many customers made substantial enhancements to these programs, some of which were incorporated into the official product. Far more installations made use of HASP than ASP, and in contemporary z/OS systems there are many more JES2 installations than JES3.
Read more about this topic: Job Entry Subsystem 2/3
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