IBM Administrative Terminal System

The Administrative Terminal System, also known as ATS/360, was an IBM contributed program which provided, for the end-user customer of IBM System/360 systems, a system which was quite similar to the proprietary IBM Service Bureau Corporation product.

Initially, ATS/360 supported only IBM 2741 terminals. Later, support was added by user groups for 2741 terminals with the "break feature" and for IBM 1050 terminals.

ATS/360 was designed exclusively for IBM 2311 and 2314 direct access storage facilities (for "working storage" and "permanent storage") and IBM 2400/3400 tape drives (for "offline storage" and for offline "format and print" tasks).

An IBM program RPQ added support for IBM 3330 direct access storage facilities, and this RPQ was applied by most users of ATS/360 which had migrated to IBM System/370 processors.

Support beyond SVS was not offered by IBM, but Peter Haas, formerly with Litton Systems Inc, and later with Amdahl Corp, added support for MVS in general, and APs and MPs in particular, and a large number of ATS/360 systems thereby remained in use well into the MVS/370 era.

ATS/360 was very parsimonious in its use of main storage, and it was not uncommon to support quite a few terminals in a minimum size region.

ATS/360 was also very parsimonious in its use of system resources, and it had its own task dispatcher which worked seamlessly with PCP, MFT/MFT-II and MVT, and, later, with MVS.

All ATS/360 input/output operations utilized EXCP exclusively, and task switching was accomplished asynchronously as an extension of the various EXCP appendages and synchronously as an extension of ATS's Type 1 SVC, SVC 255.