ITEM: BS6604L
How do I control numerous TTY-OVERRUN ERROR ID: 9D30B78E
ENV:
Machine Type(s): 7013___________________(7013, e.g. )
Machine Model(s): 590_______________________(560, e.g. )
Machine Serial(s): _26-41719______________________(serial number(s) )
Number of Users: _10______________________(total and active if relevant)
AIX Level: 3.2.5__________________________(3.2.4, 3.2.5, 4.1.1, ... )
Relevant PTFs: nfs U491130___________(e.g., for a DCE problem it )
____U428287_______________ matters what DCE PTFs are )
____u428288______________________ applied )
DESC:
I get massive errpt entries like this
---------------------------------------------------------------------------
ERROR LABEL: TTY_OVERRUN
ERROR ID: 9D30B78E
Date/Time: Thu Jan 9 11:35:07
Sequence Number: 1835570
Machine Id: 000028437000
Node Id: S7352c
Error Class: S
Error Type: TEMP
Resource Name: tty1
Error Description
Receiver over-run on input
Failure Causes
EXCESSIVE LOAD ON PROCESSOR
Recommended Actions
Reduce system load.
Reduce serial port baud rate
---------------------------------------------------------------------------
My hardware is this:
cxma0 00-06 128-Port Asynchronous Adapter
Part Number.................051G8924
EC Level....................D18445
FRU Number..................051G8925
Manufacturer................AUS1391615
Diagnostic Level............00
Device Driver Level.........00
Loadable Microcode Level....00
ROS Level and ID............000D
Serial Number...............00011336
Displayable Message.........IBM 128 PORT ASYNC CONTRO
sa2 00-06-11 16-Port RAN EIA-232 for 128-Port
Adapter
Part Number.................051G8924
EC Level....................D18445
FRU Number..................051G8925
Manufacturer................AUS1391615
Diagnostic Level............00
Device Driver Level.........00
Loadable Microcode Level....00
ROS Level and ID............000D
Serial Number...............00011336
Displayable Message.........IBM 128 PORT ASYNC CONTRO
tty1 00-06-11-00 Asynchronous Terminal
tty2 00-06-11-01 Asynchronous Terminal
tty3 00-06-11-02 Asynchronous Terminal
tty4 00-06-11-03 Asynchronous Terminal
tty5 00-06-11-04 Asynchronous Terminal
tty6 00-06-11-05 Asynchronous Terminal
tty7 00-06-11-06 Asynchronous Terminal
tty8 00-06-11-07 Asynchronous Terminal
tty9 00-06-11-08 Asynchronous Terminal
tty10 00-06-11-09 Asynchronous Terminal
tty11 00-06-11-10 Asynchronous Terminal
tty12 00-06-11-11 Asynchronous Terminal
tty13 00-06-11-12 Asynchronous Terminal
tty14 00-06-11-13 Asynchronous Terminal
tty15 00-06-11-14 Asynchronous Terminal
tty16 00-06-11-15 Asynchronous Terminal
scsi1 00-08 SCSI I/O Controller
Device Driver Level.........00
Diagnostic Level............03
Displayable Message.........SCSI-2
EC Level....................D18762
FRU Number.................. 52G7509
Manufacturer................IBM97N
Part Number................. 52G7504
Serial Number...............00018401
Loadable Microcode Level....00A0
ROS Level and ID............0009
Read/Write Register Ptr.....0100
Checked existing and outstanding APARS and Fixes
Checked info for solutions, and found little to assist.
This machines purpose is to pump data (BNU) via and X25 network to our stores.
I gotta know the data is good...
ACT:
In AIX 3.2.5 data coming into a serial port is taken by the device
driver and stored into a buffer in the kernel (called the ihog)
which by default is 512 bytes in size. The data is stored in this
buffer until a user process comes along and reads the data. However,
if data (noise, actual data, etc.) comes into the serial port but
no user process comes along to read it and data continues to come in,
then the buffer fills and is flushed and the error you are seeing is
logged.
1) If there is a process reading the data, then it is generally a flow
control problem - the data is coming in but filling the buffer
faster than the process can come along and read it.
2) If there is no process running, then either whatever is attached to
the serial port is sending data that nothing tries to read or there is
line noise.
You can reduce the number of occurrences of the error by increasing
the size of the ihog buffer from 512 bytes to a larger size:
stty ihog 2048 \< /dev/tty\#\#
If your situation is 1) then this may resolve the problem. If the
situation is 2) then this will only decrease the frequency at which
the error occurs since more "noise" can come in on the port before
the buffer has to be flushed and the error logged.
Check for U435110, a major update to the tty subsystem. Verify
flow control settings. Use RTS/CTS for ttys whenever possible
(ie the device attached permits RTS/CTS flow control).
Since this looks to be an X.25 connection to a pad, I suspect that
the PAD may be sending "heartbeat" type signals to indicate that it is
alive but the AIX software expected to be reading the data may not be
running at the time.
Support Line: How do I control numerous TTY-OVERRUN ERROR ID: 9D30B78E ITEM: BS6604L
Dated: January 1997 Category: N/A
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