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Introduction to Debugging
The VM/370 Control Program manages the resources of a single computer
such that multiple computing systems appear to exist. Each "virtual computing system,!! or virtual machine, is the functional equivalent of
an IBM System/370. Therefore, the person trying to determine the cause
of a VM/370 software problem must consider three separate areas:
1. The Control Program (CP), which controls the resources of the real
2. The virtual machine operating system running under the control of CP, such as CMS, RSCS, OS, or 3. The problem program, which executes under the control of a virtual
machine operating Information that explains how to debug CP or CMS is contained in this
book; information explaining how to debug applications programs is in
the VMLJ70 For information that explains how to use
the VM/370 Interactive Problem Control System (IPCS) for debugging,
refer to the (IPCS) If an IPCS problem is caused by a virtual machine operating system
(other than CMS and RSCS), refer to the publications pertaining to that
operating system for specific information. However, use the CP debugging
facilities, such as the CP commands, to perform the recommended
debugging procedures discussed in the other publication.
If it becomes necessary to apply a PTF (program Temporary Fix) to a
component of VM/370, refer to the VMLJ70 for detailed information on applying PTFs,. How to Start Debugging
Before you can correct any problem
you must recognize that one existse Next, you must identify the problem, collect informaticn, and determine
the cause so that the problem can be fixed. When running VM/370
must also decide whether the problem is in CP, the virtual machine, or
the problem program.
A good approach to debugging is: 1. Recognize that a problem exists.
2. Identify the problem type and the area affected.
3. Analyze the data you have available, collect more data if you need
it, then isolate the data that pertains to your problem.
4. Finally, determine the cause of the problem and correct it. Part 1. Debugging with VM/370 3
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