z/VM: CP Commands and Utilities Reference - z/VM - IBM

SET CONCEAL
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Set
Authorization
Purpose
CONCeal
Operands
Usage Notes
ON
OFF
Privilege Class: G
Use SET CONCEAL to turn on and off the protected application environment. This
environment protects a session from unexpectedly entering CP READ.
ON
SET CONCEAL
specifies that the virtual machine is to operate in the protected application
environment. This environment is intended for the application end user who
does not want to interact with CP. Instead of presenting the user with an
unexpected CP READ on occurrence of certain error conditions (for example,
paging error, soft abend, disabled wait PSW loaded), the protected application
facility forces an automatic re-IPL of the virtual machine without issuing any
error messages to the user. The IPL is initiated using the IPL command last
used for the virtual machine.
To prevent a re-IPL loop, CP does not force re-IPL if a previous automatic
re-IPL occurred less than a minute before. No more than ten automatic re-IPLs
are attempted between activation and deactivation of the protected application
environment. If a re-IPL is not attempted or if the attempt fails, CP issues the
same message as when the protected application environment is not active and
puts the terminal into CP READ state. For 3270 terminals, SET CONCEAL ON
disables the break key. If you subsequently deactivate the protected application
environment using the SET CONCEAL OFF command, the break key and the
PA1 key are reenabled. You may also enable the break key by issuing a
TERMINAL BRKKEY command while in the protected application environment.
OFF
specifies that the virtual machine should no longer operate in the protected
application environment. Certain error conditions (such as a paging error, a soft
abend, or a disabled wait PSW in the virtual processor) cause CP to take
control of the virtual machine and display CP READ on the terminal. No re-IPL
is initiated. The terminal break key, PA1 key, and ASCII double break or
attention are reenabled when you enter SET CONCEAL OFF.
1. With your break key disabled, you cannot enter the CP READ state while
running in full screen mode unless your guest (operating system or application)
provides a way. The guest can use DIAGNOSE X'08' to pass either the CP
command or no command at all to enter CP READ. In addition, the TERMINAL
MODE command allows entry to CP on a console attention interrupt when in
line mode.
2. An application can establish the protected application environment for itself by
issuing a SET CONCEAL ON command using DIAGNOSE X'08'.
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Chapter 2. CP Commands 1207