Specifications

Debugging and Testing Tools

9.2 OpenVMS Delta/XDelta Debugger

The OpenVMS Delta/XDelta Debugger (DELTA/XDELTA) is a primitive debugger.

It is used to debug code that cannot be debugged with the symbolic debugger, that

is, any code that executes at interrupt priority levels (IPLs) above IPL0 or any

code that executes in supervisor, executive, or kernel mode. Examples include

user-written device drivers and the OpenVMS operating system.

Almost all the commands available on DELTA are also available on XDELTA.

Furthermore, both DELTA and XDELTA use the same expressions. However,

they are different in two ways: you use them to debug different kinds of code,

and you invoke and exit from them in different ways.

You can use DELTA to debug programs that execute at IPL0 in any processor

mode (user, supervisor, executive, and kernel). You can also debug user-mode

programs with DELTA, but the debugger is more suitable. To run DELTA in a

processor mode other than user mode, your process must have the privilege that

allows DELTA to change to that mode—change-mode-to-executive (CMEXEC) or

change-mode-to-kernel (CMKRNL) privilege. You cannot use DELTA to debug

code that executes at an elevated IPL.

You can use XDELTA to debug programs that execute in any processor mode and

at any IPL. To use XDELTA, you must have system privileges, and you must

include XDELTA when you boot the system.

You can use DELTA/XDELTA commands to perform the following debugging

tasks:

• Open, display, and change the value of a particular location

• Set, clear, and display breakpoints

• Set display modes in byte, word, longword, or ASCII

• Display instructions

• Execute the program in a single step with the option to step over a subroutine

• Set base registers

• List the names and locations of all loaded modules of the executive

For more information about using DELTA/XDELTA for debugging, see the

OpenVMS Delta/XDelta Debugger Manual.

9.3 OpenVMS AXP System-Code Debugger (AXP Only)

AXP

OpenVMS AXP supports a new symbolic debugger that can be used to debug

nonpageable system code and device drivers running at any IPL. The OpenVMS

AXP System-Code Debugger lets you use the familiar OpenVMS Debugger

interface to observe and manipulate system code interactively as it executes.

Using the OpenVMS AXP System-Code Debugger, you can perform the following

tasks:

• Control the system software’s execution—-stop at points of interest, resume

execution, intercept fatal exceptions, and so on

• Trace the execution path of the system software

• Monitor exception conditions

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