1) Allocate a PS dataset. DCB characteristics don't matter unless
you specify a BLKSIZE. If you do, make it 4096. The other DCB
characteristics will be overwritten. Best way to do this is to
issue these commands from TSO READY or ISPF Option 6:
ALLOC FILE(X) DA(...dsn...) NEW CAT TRACKS SPA(15) DSORG(PS)
This will allocate a dataset with no DCB characteristics. Be
sure to specify enough space for the trace. There is no point
in specifying secondary space. APPC will only use the primary
space allocation wrapping back to the front when it hits the
end of the primary space.
2) Make sure that the client address space and the server address
space have UPDATE access to the trace dataset. The client is
the TSO session that initiates the IOF session. The server is
the transaction processor address space which is initiated when
the AT command is issued. Both should normally have the same
userid environment, so as long as the TSO session can update the
dataset, the server should be ok also.
Additionally, the APPC address space also needs access to the
dataset. If this is a RACF system, then this should occur
automatically. If not RACF, then you might have to do something
to set this up.
3) Issue the Rexx exec ATBTRACE with the following parms:
ATBTRACE START DA(Step #1 DSN) LU(partner_LU) TP(APPC_TP_name)
Basically, the partner_LU is the LU name defined in the B67
option member and APPCTP_name is the transaction processor
name define in B67. You can also add the USERID parameter to
filter the tracing down to APPC sessions that involve that userid.
The syntax of the USERID parameter is as follows:
ATBTRACE causes APPC to trace the side of the conversation that
is on this CPU. If both sides of the conversation are on the
same CPU, then you will see both sides of the conversation.
Also, it appears that to capture a trace, you need to issue the
ATBTRACE command prior to initiating the APPC session. You can't
get into an APPC session and then start tracing.
4) Run the APPC function to be traced.
5) Issue the Rexx exec ATBTRACE with the following parms:
ATBTRACE STOP DA(Step #1 DSN)
6) Read the dataset, it is in text format.
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