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Diagnostics via VTAM and NCP Traces
Overview
When diagnosing problems on an SNA network
involving JBM Electronics' Gateways connected to an IBM 37xx FEP, a VTAM buffer or line trace can
be an invaluable aid. Assume a simple network configuration such as the one shown below:
A line trace between the 37XX and the JBM
device can help identify problems related to misconfigurations on either the host computer or at
the IBM device or reveal incompatibilities which can be resolved by software modifications at the
Gateway device. The important thing to keep in mind is that the trace must be captured
between the 37XX and the Gateway and not between VTAM and NCP at the 37XX.
Trace Procedures
Producing a trace involves three major steps:
- Starting the Generalized Trace Facility (GTF)
This document assumes you have established data sets on
your system to hold the records captured and processed
by GTF. Instructions to perform this are
system specific and beyond the scope of this document. An example of starting and stopping GTF, and
specifying options is provided later in this document.
- Capturing the trace records
This involves using VTAM MODFIY commands to
start and stop trace capture, details are illustrated later in this document. It is important
to remember to start the trace some time before the problem to be captured occurs so that we can see
the sequence of events leading up to the problem. It some circumstances it may be wise to
have the device or resource of interest in an inactive state and then activate it once the trace starts,
in order to reveal any problems which may be related to initialization or start-up conditions.
Starting a trace after a problem has already occurred often does not reveal any useful
information.
- Formatting and printing the trace
The IBM product ACF/TAP is generally used to format
and print traces.
| Note: |
The specific syntax to perform these
operations may be dependent on your particular hardware and software configuration; therefore,
the commands we provide may not work exactly on your system, they are provided only to illustrate
the general series of steps involved. |
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You may need to adjust the syntax to suit
your system; your network operations staff should be able to provide support towards this end.
Detailed information pertaining to VTAM operations is found in IBM publication SC31-6549-00 -
VTAM V4R3 for MVS/ESA Operations or online, by clicking
here.
|
| Operation |
Command |
| Start GTF |
S GTF.JBM1 (where JBM1 is a unique identifier) |
| A reply similar to the following is returned: |
00 AHL100A SPECIFY TRACE OPTIONS |
| Respond to this message as follows: |
00,TRACE=USRP |
| A reply similar to the following is returned: |
AHL103I TRACE OPTIONS SELECTED--USRP
01 AHL125A RESPECIFY TRACE OPTIONS OR REPLY U |
| To capture VTAM buffer trace, respond: |
01,USR=(FF1,FEF) |
| To capture VTAM line trace, respond: |
01,USR=(FF2,FE4) |
| To capture VTAM line trace, respond: |
01,USR=(FF2,FE4) |
| A reply similar to the following is returned: |
02 AHL102 CONTINUE TRACE DEFINITIONS OR REPLY END |
| Respond to this message with: |
02,END |
| A reply similar to the following is returned: |
03 AHL125A RESPECIFY TRACE OPTIONS OR REPLY U |
| Respond to this message with: |
03,U |
Note: The reply message is
preceded by a response number (shown in bold) which is used as an identifier when
responding.
Additional information on GTF may be
found by clicking
here.
| Operation |
Command |
| Start a VTAM buffer trace |
F NET,TRACE,ID=resource name,type=BUF,IDtype=RESOURCE |
| Stop a VTAM buffer trace |
F NET,NOTRACE,ID=resource name,type=BUF,IDtype=RESOURCE |
| Start a VTAM line trace |
F NET,TRACE,type=LINE,ID=line name,COUNT=ALL |
| Stop a VTAM line trace |
F NET,NOTRACE,type=LINE,ID=line name,COUNT=ALL |
| Operation |
Command |
| Stop GTF |
P GTF |
The trace is printed via the services of
AFC/TAP. An example of a common setup is as follows:
//ACFTAP EXEC PGM=ACFTAP
//STEPLIB DD DSN=ACFNCP21.IPO.SYSLIB,DISP=SHR
//SYSLDPRT DD SYSOUT=A,HOLD=YES
//SYSLSPRT DD SYSOUT=A,HOLD=YES
//SYSSDPRT DD SYSOUT=A,HOLD=YES
//SYSSSPRT DD SYSOUT=A,HOLD=YES
//SYSNEPRT DD SYSOUT=A,HOLD=YES
//SYSDTPRT DD SYSOUT=A,HOLD=YES
//SYSBFPRT DD SYSOUT=A,HOLD=YES
//SYSPRINT DD SYSOUT=A,HOLD=YES
//SYSTRACE DD UNIT=SYSDA,DSN=SYS1.GTFNCP,VOLSER=WORK01,DISP=OLD
//SYSIN DD *
INPUT=LINE
SOURCE=GTF
LSPRT=YES
LDPRT=ERROR
SSPRT=YES
SDPRT=YES
NEPRT=YES
STIME=
ETIME=
/*
Again, the specific syntax to perform these
operations may be dependent on your particular hardware and software configuration. Hopefully,
this document provides enough general information for you to make the right choices on your system.
Please feel free to contact us if you have questions or comments, or can provide information to make this
document more useful. You can call or e-mail us
at: support@jbmelectronics.com
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