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  • 1.  What causes TTY_TTYHOG error?

    Posted 02/16/07 09:52 AM

    Originally posted by: ccompton



    For a few minutes yesterday I got the following entries in the error log.
    I've not seen them before in the several years this system has been running.
    Any ideas what the root causes could be?

    LABEL: TTY_TTYHOG
    IDENTIFIER: 0873CF9F

    Description
    TTYHOG OVER-RUN
    ....
    Failure Causes
    EXCESSIVE LOAD ON PROCESSOR

    Recommended Actions
    REDUCE SYSTEM LOAD.
    REDUCE SERIAL PORT BAUD RATE

    #AIX-Forum


  • 2.  Re: What causes TTY_TTYHOG error?

    Posted 02/16/07 10:16 AM

    Originally posted by: SystemAdmin


    In the past I've seen this with poor wiring. Sometimes slowing the baud rate down can fix this, sometimes you need better cables or the grounding has been done wrong.

    The canned IBM response to this appears to be:

    Most PMRs attribute the error message as the result of flow control
    problem.
    .
    The error TTY_TTYHOG indicates that the sending device is ignoring flow
    control. This error occurs after the hardware FIFO has been accessed and
    has written to the software buffer.
    .
    In other words, the tty hog error is logged because the buffer where
    incoming characters are placed is overflowing. When the buffer is about
    3/4's full, the device driver notifies the hardware , to send the XOFF
    char to the sender to stop send data (or drop the hardware control line)
    . If the sender continues to send data, and the buffer is not emptied,
    the device driver flushes the buffer and logs the error message in the
    error log.
    .
    For example, say in a telnet session we enter more than 512 characters
    and hit enter. We could fill up our recv buffer on the adapter and the
    device driver will send su the XOFF command. However, if we ignore this
    and continue to send the block data, we will log this error in errpt.
    .
    The end point is this is a problem on a client system. It is a temporary
    error and there isnt' anything that we will be able to do about if from
    a AIX point of view
    .
    Suggestions
    • check cabling
    • enable flow control on client
    • update bos.rte.tty to last version

    #AIX-Forum