AS/400 Communication Trace

[hbmedp@xxxxxxxxxxxx]

Hi,

We are running on V3R6 on a PowerPC 530-2153 box, recently one of our 
online applications encountered a problem on its ASYNC communication line 
which caused the driver program to abend. There was no link interruption 
at that time and the ASYNC line, controller remained in ACTIVE status while 
the device was in VARIED ON status - as the driver program had abended. We 
managed to capture a communication trace using SST and found that messages 
were split into two parts when there were received at the AS/400 though the 
datascope trace (taken from a data analyzer connected on the AS/400 ASYNC 
line) showed that continuous full messages were being sent by the 
originating Host at the other end. This is acceptable as long as the two 
blocks are sent by the AS/400 to the application within a time limit - we 
suspect it is controlled by the IDLTMR (specified in the AS/400 ASYNC line 
description). However, there were instances where the second block was 
received after the IDLTMR had expired and as a result, a single continuous 
message was processed as two separate incomplete messages - causing our 
application driver to abend. 

The IDLTMR was changed from 1 (or 0.5 seconds) to 4 (or 2 seconds) which 
seem to improve the situation as the link became more stable. However, we 
are unsure whether the IDLTMR is the actual cause of the problem and would 
appreciate if anyone out there can advise the following :

1. Why does the AS/400 spilt each incoming message into two parts although 
   it was sent as one continuous datastream without any break in   
   transmission?
2. What is the actual function of the IDLTMR? 
3. From the enclosed comm trace, how do we interprete the Record Timer? 
   Is it in seconds, milliseconds and is this related to the IDLTM setting?


Thank You.

SC Loo
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