Aug 1, 1979 COMMANDS TO COLLECT AND ANALYZE SYSTEM INFORMATION This section discusses five commands to collect and analyze
information when you are debugging. These are the ADSTOP and
commands and the LOCATE, MONITOR, and TRACE commands.
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The ADS TOP command stops the execution of a virtual machine at a
specific address; causes the virtual machine to resume execution.
Execution halts when the instruction at the address specified in the ADSTOP command is reached. At this point, you may invoke other CP debugging commands.
The address stop should be set after the program is loaded but before
it executes. When the specified location is reached during program
execution, execution halts and the CP command environment is entered. You may then enter other CP commands to examine and alter the status of
the program. Set an address stop at a location where you suspect the error in the
program. You can then display the registers, control words, and data
areas to check the program at that point in its execution. This
procedure helps you locate program errors. You may be able to alter the
contents of storage in such a way that the program will execute
correctly. You can then correct the error you have detected and, if
necessary, compile and execute the program again.
To successfully set an address stop, the virtual instruction address
must be in real storage at the time the ADSTOP command is issued. Use the LOCATE command to find the address of CP control blocks
associated with a particular user, a user's device, or a real system
device. The control blocks and their functions are described in the XnLllQ £Qnt£Ql Blg£! Logic. Once you know the location of the control blocks, you can examine (DUMP or DISPLAY) the block you want to look at. When you want to
examine specific control blocks, use the LOCATE and DUMP or DISPLAY commands to examine the control blocks instead of taking a dump. A
discussion of the most important fields of the VMBLOK, VCUBLOK, VDEVBLOK, RCHBLOK, RCUBLOK, and RDEVBLOK are included in "Reading CP Abend Dumps." COMMANDS THAT TRACE EVENTS IN VIRTUAL MACHINES Use the TRACE command to trace the following virtual machine events: SVC interruption I/O interruption Program interruption External interruption 40 System Programmer's Guide
Page of GC20-1807-7 As Updated Aug 1, 1979 by TNL GN25-0492 Non-I/O privileged instructions 510, 5IOF, TIO, CLRIO, HIO, HDV, and TCH instructions. Branch instructions CCW and C5W instructions
The results collected by the TRACE command are spooled to your virtual
printer and to your terminal and/or real printer. Part 1. Debugging with VM/370 40.1
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