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4.2.3.6 Controlling the Terminal Keyboard

 






   In order for Session Manager to update your display screen, TSO/E requires 
   that the terminal keyboard remain locked. When the keyboard is locked, you 
   cannot enter commands, and attention interruptions will not be processed. 
   The CONTROL operand of the CHANGE.TERMINAL command lets you specify the 
   number of seconds the keyboard is to be locked while a command is 
   executing or while Session Manager is updating the screen. CONTROL can be 
   any integer from 0 to 999. 



   If you want to wait for each TSO/E command or program to execute and have 
   its output displayed before entering the next command, set CONTROL to a 
   very high value. Note that attention interruptions will not be processed 
   while the keyboard is locked. 



   If you want to enter TSO/E or Session Manager commands before the 
   currently executing command has completed, set CONTROL to 0. The keyboard 
   unlocks immediately after Session Manager rewrites the screen and you can 
   then enter new commands. However, Session Manager only updates the screen 
   after you have pressed the Enter key or any PF key. You must press the 
   Enter key or a PF key every time you want new output from a command or 
   program displayed. 



   Specifying CONTROL as a small number (10 to 20) is a compromise between 
   the two extremes. A number in that range allows most TSO/E commands time 
   to execute and have their output displayed, yet does not cause the 
   terminal keyboard to be locked for long periods of time. 



   In the IBM-supplied default environment, the keyboard locks for a maximum 
   of 15 seconds. The scrolling PF keys reset the CONTROL timer to 0 so that 
   the keyboard immediately unlocks when you press one of them. PF key 12 (or 
   24) resets the CONTROL operand to the last non-zero value it had. This is 
   done to allow you to scroll back and review previous information in a 
   stream while a TSO/E command is executing without waiting for the command 
   or program to complete. 





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