TechInfo:OS:IBM Mainframes:MFT/MVT/MVS console operations

From neurotica.com

When the display fills up (and you haven't reconfigured the settings as shown below) you need to clear the current messages before the system will continue. Type K (an abbreviation for the CONTROL command) and hit <Enter>. The line will be replaced by this:

   K E,1,9

This is the command to delete any unimportant lines between lines 1 and 9 of the display. Those lines will be marked with "|" characters at the beginning to show that they are unimportant and will be cleared. hit <Enter> to execute the command. Some lines (including those beginning with "*" to indicate that they require operator attention) are "important" and will not be cleared. See lower down for how to get rid of these. The console will, by default, use a group of lines somewhere in the middle for a "display". Various options of the DISPLAY command (abbreviation D) use this area for their output. For example, the command D C,K shows help information about the K (CONTROL) command options. Those lines remain in that area while other lines appear around them. You can remove this display area with the command K E,D. You can prevent the display area from ever reappearing with the command K A,NONE. After that, commands which would have used the display area just scroll information on the display along with other output. This is useful for commands like D U (short for DISPLAY UNITS) which shows lots of lines of information about all the units connected to the system. Reconfigure the terminal's display settings with this command:

   K S

which makes a pre-prepared line with the current settings appear, editing that line and hitting <Enter> will make the new settings take effect. A convenient configuration recommended by Jay Maynard is:

   K S,DEL=RD,RNUM=19,CON=N,SEG=19,RTME=001

"RD" is roll-delete mode, in which unimportant messages will scroll off the screen without explicit action. PF key definitions are created like this:

   K N,PFK=(num,CMD=command),CON=N

After executing this command, hitting PFnum will execute the configured command. "CON=N" tells the system to execute the command immediately rather than insert it into the command line for possible editing. A useful example is:

   K N,PFK=(1,CMD='K E,1'),CON=N

which executes "K E,1" when PF1 is pressed. This command:

   D PFK

displays current PK key definitions. If you haven't done a K A,NONE to remove the display area then you can do D ...,L=Z to display them inline.

This information was adapted from an original document by Malcolm Beattie <mbeattie@clueful.co.uk>.