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Debug Input/Output: The System Console

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Under normal circumstances, Debug Input/Output is typically directed to the user's terminal. However, during the following occasions, Debug I/O is redirected to the MPE XL system console:

  • During the bootstrap process (until the system is up), all Debug I/O is directed to the system console.

  • All system process debugging uses the system console.

  • All job debugging uses the system console. The environment variable JOB_DEBUG allows jobs to enter Debug.

  • The environment variable CONSOLE_DEBUG can be used to cause all processes that are entering Debug for the first time to use the system console.

  • The environment variable CONSOLE_IO can be used to cause all debugging for the current process to be directed to the system console.

  • The environment variable TERM_LDEV allows the use of any terminal for debugging. A privileged procedure, DEBUG_AT_LDEV (ldev : ldev_type), is also available to enter the debugger and direct I/O to the specified terminal LDEV.

When Debug is using the system console, the following technique is recommended to prevent confusion while sharing the console with the CI: 

   $cmdebug > :restore
Running RESTORE prevents unwanted terminal reads from the console's CI.

See the ENV command for detailed descriptions of all of the environment variables mentioned above.



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