This appendix describes how to use SNATRACE, a software tool that captures SDLC and Token-Ring information for a specified 3270/SNA service, and writes the information into the service's log file. SNATRACE is useful for analyzing problems such as line errors, and incorrect information in the 3270/SNA service, NCP, or VTAM configurations. Topics presented are as follows:
Who should use SNATRACE Using SNATRACE What SNATRACE captures Viewing SNATRACE information
To interpret the information that SNATRACE provides, you need an understanding of SNA and 3270 data streams. The information that SNATRACE provides, along with your level of experience and site-specific information, can help you determine what action to take.
You issue the SNATRACE command from DOS. Only one 3270/SNA service per server may be traced at a time. The syntax of the SNATRACE command is as follows:
SNATRACE [switch] [service-name]
where service-name specifies a 3270/SNA service, and switch can be one of the following:
-o tells the service to start tracing.
-f tells the service to stop tracing and write SNATRACE information to the service log.
-d tells the service to delete all existing SNATRACE information from the service log.
Note: Do not run SNATRACE any longer than you must. When run over a lengthy period of time, SNATRACE adversely affects 3270/SNA service performance, and consumes large amounts of disk space.
Before you begin the current trace, you might consider using the -d switch to delete SNATRACE information from previous traces from the service log. This helps you identify information from the current trace.
While you run a trace, you should attempt to initiate 3270/SNA sessions with the host. This helps you isolate the cause of communications problems.
The following example shows a sequence of SNATRACE commands that delete existing SNATRACE information, start a trace, and write SNATRACE information into the log file for the service.
snatrace -d host1@sna@servers
snatrace -o host1@sna@servers
snatrace -f host1@sna@servers
SNATRACE captures the contents of SDLC and Token-Ring packets (also referred to as Basic Link Units) in hexadecimal format while the trace is running. SDLC and Token-Ring packets contain the following SDLC and SNA components:
Link Header (LH)
Transmission Header (TH)
Response Header (RH)
Request/Response Unit (RU)
Link Trailer (LT)
SNATRACE also captures all SNA BIND, ACTLU, and ACTPU sequences if you initiate the trace immediately after you start the 3270/SNA service, or if a line reset occurs while the trace is running. A line reset occurs when the host sends an SDLC Set Normal Response Mode (SNRM) command.
SNATRACE information appears in the 3270/SNA service log. Instructions on accessing logs appear in the Server Operations Guide.
When you analyze SNATRACE information, some key questions to ask yourself include:
Is the service responding correctly to all ACTPU and ACTLU sequences? Is the service accepting all BIND requests? Is the service receiving session-limit-exceeded errors from the host?