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The concept of transient area is part of [[The Mythical Man-Month|Mythical Man-Month]]'s discussion on design and the use of main memory.<ref>{{cite book
|title=The Mythical Man-Month |year=1975 |page=101
|author=F. P. Brooks |isbn=0-201-00650-2}}</ref> To further reduce memory usage, the supervisor employed overlays called ''transients'' that were read into one of two reserved ''transient areas'' as required.
* Physical transients were loaded into the 556 byte A-Transient area to handle hardware errors (ERPs), record error-specific data (OBR/MDR) on IJSYSRC, and issue error messages. All A-Transient module names began with $$A.
* Logical transients were loaded into the 1200 byte B-Transient area to provided common program services like OPEN and CLOSE for LIOCS. All B-Transient module names began with $$B.
The use of $$A and $$B prefixes ensured rapid loading of transients because their names were stored first in the directory.
DOS/VS added Machine Check and Channel Check Handlers, which were another set of transients all starting with $$RAST and executing in the Recovery Transient area. This was done as part of the reliability, availability, and serviceability (RAS) enhancements for the System/370. Before this addition, machine checks caused termination of the program running and channel checks caused termination of the program accessing the device, at the time of the error. [[User:WarrenFW|WarrenFW]] ([[User talk:WarrenFW|talk]]) 23:48, 24 September 2020 (UTC)
===Multiprogramming===
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