ITEM: FX6366L

SNA sending SIGUSR1 to a process group

QUESTION:

   ENV: AIX 4.2.1, SNA 3.1.2.0, token ring

   The customer's SNA Transaction Program is receiving a SIGUSR1
   causing it to be killed.  Other processes in the same process
   group are being killed also.  Why is this happening?  What can be
   done about it?

ANSWER:

   How the SIGUSR1 issue works:  When a TP makes an open to sna,
   sna takes note of the process group of that TP.  If the linkstation
   or session being used by the TP drops, sna will send a SIGUSR1
   signal to that process group.  Customers can tell which process
   group the process is in by issuing:

           ps -eo pid,pgid,args

   All processes in the process group will be killed as a result of
   the SIGUSR1.  To isolate the TP from other processes, the customer
   can use the "setpgid" function call in their program BEFORE making
   the open to sna call.  This "setpgid" function is an AIX function
   that will give the TP a unique process group id.  Then when sna
   issues the SIGUSR1 to that process group, the TP will be the
   only process in the group and will be the only one affected.

   All TPs written to the OLD api will behave this way regardless
   of which version of SNA they are running under.  However,
   NEW TPs written to the NEW api will not behave this way.




Support Line: SNA sending SIGUSR1 to a process group ITEM: FX6366L

Dated: June 1998 Category: N/A

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