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  • keep-alive in sqlhosts [39810]

    From Habichtsberg, Reinhard@21:1/5 to Reinhard on Tue Sep 5 16:53:37 2017
    To: informix-list@iiug.org (informix-list@iiug.org)

    Fernando, Andreas,

    we use Solaris 10 and as you said the interval is 2H. The command to show is /usr/sbin/ndd -get /dev/tcp tcp_keepalive_interval. You will see milliseconds. In our case 7200000.

    Yes, we'll try it. k=1 is part of the comma separated options list in fifth column of sqlhosts.

    Thanks,

    Reinhard  Habichtsberg
    Dienstleistungsverantwortlicher IT-Rechenzentrum
    Solaris- und Datenbanksysteme
    Abrechnungszentrum Emmendingen
    Tel.: 07641/9201-203


    -----Ursprüngliche Nachricht-----
    Von: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org] Im Auftrag von Fernando Nunes
    Gesendet: Dienstag, 5. September 2017 17:17
    An: ids@iiug.org
    Betreff: Re: keep-alive in sqlhosts [39810]

    It will solve the issue (unless the firewall is configured to ignore it, but I've never seen any case of that).
    HOWEVER... the option in Informix side "asks" the OS to send the probes.
    When (with which interval), the answer timeout etc. is entirely the OS responsability... and in many situations the defaults are around 2H, and most situations I've seen the firewalls "kill" the connections after 1H...
    if you find yourself into this situation, the feeling you'll get it that it didn't work... when in fact it's just misconfiguration.

    You should check the OS documentation on how to configure the keep alive functionality... I've been involved in linux and hp-ux in the past... but if you need assistance, please tell us your OS.

    Note that after you change SQLHOSTS you need to at least restart the listener (if your Informix version has this functionality). Checking if the option is in effect can be trivial (lsof) in most operating systems, but is nearly a nightmare on Linux...
    one option is to compile and load a kernel module.... but I always have the feeling there's another option, which I never remember... maybe some obscure option of netstat... another option would be to sniff the trafic...

    Regards.

    On Tue, Sep 5, 2017 at 12:59 PM, Habichtsberg, Reinhard < RHabichtsberg@arz-emmendingen.de> wrote:

    Hi all,

    we have the problem that longer lasting remote client sessions on
    informix databases are interrupted by the firewalls, particulary when
    no packets were sent. It's possible to configure the port on the
    firewall to extend the time before the connection is interrupted. The disadvantage is that you never know if the time you choose is long
    enough or if you found all database-server ports.

    We found a parameter which can be set in the sqlhosts file of the
    server, if I understand aright.

    From http://www-01.ibm.com/support/docview.wss?uid=swg21160988

    To enable the keep-alive option for an Informix database server TCP
    port, specify k=1 in the fifth column of the related line of the
    server in the sqlhosts file. The following table is a summary of
    possible setting of the keep-alive option in an IBM Informix server sqlhosts file and its results.
    k setting in the options field Result

    k=0 Disables keep-alive feature: this means the local TCP driver does
    not check whether a connection is active. For example, from a PC, if
    you make a connection to an IBM Informix database server, and then
    switch off the PC, then netstat -a and onstat -u shows the TCP and
    database network connection are still established. The TCP connection
    is never terminated until stopping and restarting the Informix server.

    k=1 Enables the keep-alive feature

    My question: Does this setting solve the issue? Or can it cause
    unexpected side-effects.

    Thanks,

    Reinhard Habichtsberg
    Dienstleistungsverantwortlicher IT-Rechenzentrum
    Solaris- und Datenbanksysteme
    Abrechnungszentrum Emmendingen
    Tel.: 07641/9201-203


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    --
    Fernando Nunes
    Portugal

    http://informix-technology.blogspot.com
    My email works... but I don't check it frequently...


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