Editing DOS/360 and successors (section)

===Transients===
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 |publisher=Addison-Wesley Publishing Company |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 {{mono|$$A}}.
* Logical transients were loaded into the 1200 byte B-Transient area to provide common program services like OPEN and CLOSE for LIOCS.  All B-Transient module names began with {{mono|$$B}}.

The use of {{mono|$$A}} and {{mono|$$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 {{mono|$$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.