Steps for collecting documentation

If processing stops or TCP/IP does not respond to commands, TCP/IP might be in a loop and you can collect documentation to help diagnose the problem.

Procedure

Perform the following steps to collect documentation:

Get dump output.
Enabled
Get an SVC dump of TCP/IP or the looping TCP/IP component by issuing the DUMP command from the MVS™ system console, or press the Program Restart key. See the z/OS MVS Diagnosis: Tools and Service Aids for more information about the DUMP command.
Guidelines: Ensure that the following storage areas are dumped because they might be needed to diagnose the TCP loop:
TCP/IP and VTAM® address spaces.

SDATA options RGN, CSA, LSQA, NUC, PSA, and LPA.

CSM data spaces. Add DSPNAME=(1.CSM*) to the DUMP command to include both of them in the dump.
For examples of the DUMP command, see TCP/IP services traces and IPCS support and Diagnosing storage abends and storage growth.
Disabled
If the loop is disabled, the MVS system console is not available for input. Try the following steps:
- Use a PSW RESTART to terminate a looping task. This process creates a LOGREC entry with a completion code of X'071'. Use the LOGREC record and the RTM work area to locate the failing module. Depending on the PSW bit 32, the last 3 bytes (24-bit mode) or 4 bytes (31-bit mode) contain the address being executed at the time of the dump. Scan the dump output to find the address given in the PSW. For more information about using PSW RESTART, see z/OS Communications Server: SNA Diagnosis Vol 1, Techniques and Procedures.
- Take a stand-alone dump. See z/OS MVS Diagnosis: Tools and Service Aids for information about stand-alone dumps.
Get the MVS system console log (SYSLOG), the job log from the started procedure, and the LOGREC output.
The MVS system console log might contain information, such as error messages, that can help you diagnose the problem. Also, print the LOGREC file.

Use the LOGDATA option to print the in-core LOGREC buffers. See z/OS MVS Diagnosis: Tools and Service Aids or z/OS MVS IPCS Commands for more information about the LOGDATA option.
Tip: The SYSERROR data set might contain additional information to help you diagnose the problem.
Determine whether there are any messages associated with the loop, such as a particular message always preceding the problem, or the same message being issued repeatedly. If so, add the message IDs to your problem documentation.
Examine the trace entries using IPCS.
By examining all of the trace entries in the system trace table, you might be able to determine whether there is a loop. The most obvious loops would be a module or modules getting continual control of the TCP/IP system.

Use the PSW to determine the names of the modules in the loop. See z/OS MVS IPCS User's Guide for information about using IPCS.

In the output shown in Figure 1, the CLKC entries indicate an enabled loop. The PSW addresses on the CLKCs identify the looping program. Use the WHERE subcommand to locate the responsible program.
Figure 1. Example of output from the IPCS SYSTRACE command
```
02-0029 008E7220   CLKC      078D2600 83A8192C  00001004  00000000

02-0029 008E7220   CLKC      078D2600 83A81934  00001004  00000000
 
02-0029 008E7220   CLKC      078D2600 83A81930  00001004  00000000
 
02-0029 008E7220   CLKC      078D2600 83A8192A  00001004  00000000
 
02-0029 008E7220   CLKC      078D2600 83A81930  00001004  00000000
 
02-0029 008E7220   CLKC      078D2600 83A81938  00001004  00000000
```