Other types of trace on z/OS

There are other trace facilities available for problem determination. Use this topic to investigate channel initiator trace, line trace, CICS® adapter trace, SSL trace, and z/OS® trace.

It can be helpful to use the following trace facilities with IBM MQ .

The channel initiator trace

See Figure 3 for information about how to get a dump of the channel initiator address space. Note that dumps produced by the channel initiator do not include trace data space. The trace data space, which is called CSQXTRDS, contains trace information. We can request this by specifying it on a slip trap or when we use the dump command.

We can run the trace using the START TRACE command. We can also set this trace to start automatically using the TRAXSTR queue manager attribute. For more information about how to do this, see ALTER QMGR.

We can display this trace information by entering the IPCS command:

LIST 1000. DSPNAME(CSQXTRDS)

We can format it using the command:

CTRACE COMP(CSQXssnm)

where ssnm is the subsystem name.

The line trace

A wrap-around line trace exists for each channel. This trace is kept in a 4 KB buffer for each channel in the channel initiator address space. Trace is produced for each channel, so it is ideal for problems where a channel appears to be hung, because information can be collected about the activity of this channel long after the normal trace has wrapped.

The line trace is always active; we cannot turn it off. It is available for both LU 6.2 and TCP channels and should reduce the number of times a communications trace is required.

We can view the trace as unformatted trace that is written to CSQSNAP. We can display the trace by following these steps:

Ensure that the CHIN procedure has a SNAP DD statement.
Start a CHIN trace, specifying IFCID 202 as follows:
```
START TRACE(CHINIT) CLASS(4) IFCID(202)
```
Display the channel status for those channels for which the line trace is required:
```
DISPLAY CHSTATUS(channel) SAVED
```
This dumps the current line for the selected channels to CSQSNAP. See Snap dumps on z/OS for further information. Note:
1. The addresses of the storage dump are incorrect because the CSQXFFST mechanism takes a copy of the storage before writing it to CSQSNAP.
2. The dump to CSQSNAP is only produced the first time you run the DISPLAY CHSTATUS SAVED command. This is to prevent getting dumps each time you run the command. To obtain another dump of line trace data, you must stop and restart the current trace.
  1. We can use a selective STOP TRACE command to stop just the trace that was started to gather the line trace data. To do this, note the TRACE NUMBER assigned to the trace as shown in this example:
```
+ssid START TRACE(CHINIT) CLASS(4) IFCID(202)
     CSQW130I +ssid 'CHINIT' TRACE STARTED, ASSIGNED TRACE NUMBER 01
```
  2. To stop the trace, issue the following command:
```
+ssid STOP TRACE(CHINIT) TNO(01)
```
  3. We can then enter another START TRACE command with a DISPLAY CHSTATUS SAVED command to gather more line trace data to CSQSNAP.
The line trace buffer is unformatted. Each entry starts with a clock, followed by a time stamp, and an indication of whether this is an OUTBOUND or INBOUND flow. Use the time stamp information to find the earliest entry.

The CICS adapter trace

The CICS adapter writes entries to the CICS trace if your trace number is set to a value in the range 0 through 199 (decimal), and if either:

CICS user tracing is enabled, or
CICS internal/auxiliary trace is enabled

We can enable CICS tracing in one of two ways:

Dynamically, using the CICS-supplied transaction CETR
By ensuring that the USERTR parameter in the CICS system initialization table (SIT) is set to YES

For more information about enabling CICS trace, see the CICS Problem Determination Guide.

The CICS trace entry originating from the CICS adapter has a value AP0 000, where 000 is the hexadecimal equivalent of the decimal value of the CICS adapter trace number you specified.

The trace entries are shown in CICS adapter trace entries.

System SSL trace

We can collect System SSL trace using the SSL Started Task. The details of how to set up this task are in the System Secure Sockets Layer Programming documentation, SC24-5901. A trace file is generated for each SSLTASK running in the CHINIT address space.

z/OS traces

z/OS traces, which are common to all products operating as formal subsystems of z/OS, are available for use with IBM MQ. For information about using and interpreting this trace facility, see the MVS Diagnosis: Tools and Service Aids manual.