Undoing modifications in a window

The RESET function can be used to undo (“erase”) changes that have been made in windows since MAP or the most recent SAVE. A file region for which the RESET function is to be executed must be defined, taking the effects of the DISPOS operand of the MAP function into account:

• If the window is defined with DISPOS=*OBJECT, an access to a page following a RESET will cause that page of the file to be displayed on the screen.

• If the window is defined with DISPOS=*UNCHNG, an access to a page following a RESET will cause that page to be initialized with X'00', unless that page has already been written to the file using SAVE. In the latter case, the page is read again from the file after RESET.

List of the most important macro operands for undoing modifications in a window

Operand	Operand values	Meaning
FCT	*RESET	Undoes modifications in a window
OFFSET SPAN		The OFFSET and SPAN operands define the file area for which the RESET function is to be executed (i.e. the beginning of the area and its length in 4KB blocks). All modifications in the window pages of the RESET region are undone.
RELEASE		The RELEASE=*YES operand extends the RESET function to all pages of the specified region, not just to modified pages.