Starting z/OS Debugger at different points

If z/OS® Debugger is started during program initialization, it is started before all the instructions in the main prolog are run. At that time, no program blocks are active and references to variables in the main procedure cannot be made, compile units cannot be called, and the GOTO command cannot be used. However, references to static variables can be made.

If you enter the STEP command at this point, before entering any other commands, both program and Language Environment® initialization are completed and you are given access to all variables. You can also enter all valid commands.

If z/OS Debugger is started while your program is running (for example, by using a CEETEST call), it might not be able to find all compile units associated with your application. Compile units located in load modules that are not currently active are not known to z/OS Debugger, even if they were run prior to z/OS Debugger's initialization.

For example, suppose load module mod1 contains compile units cu1 and cu2, both compiled with the TEST option. The compile unit cu1 calls cux, contained in load module mod2, which returns after it completes processing. The compile unit cu2 contains a call to the CEETEST library service. When the call to CEETEST initializes z/OS Debugger, only cu1 and cu2 are known to z/OS Debugger. z/OS Debugger does not recognize cux.

The initial command string is run only once, when z/OS Debugger is first initialized in the process.

Commands in the preferences file are run only once, when z/OS Debugger is first initialized in the process.