Start the DEBUG facility by specifying DEBUG=YES in the initialization stream or by entering a $T command with the DEBUG=YES parameter. When you want to turn off the DEBUG facility, enter a $T DEBUG=NO command. Display the status of the DEBUG facility by entering the $D DEBUG command. JES2 responds to the $D command with message $HASP827, to display the status of DEBUG.

If an error occurs, JES2 issues a $K01 error code.

A JES2 dump contains output from the DEBUG facility. In the dump, register 1 contains the checkpoint this JES2 image expected and register 14 contains the checkpoint as it appears on the checkpoint data set. The checkpoint on the data set should enable the installation to determine the cause of the error.