Frequently Asked Questions


Product: NPort/Async Server Fixed tty driver
Company: Moxa Inc.
Revision date: 5/3/2005

Q. Open ports might fail under SCO UnixWare and SCO OpenServer if the
   maximum number of file descriptors is reached. How can I increase the
   maximum number of file descriptors to solve this problem?

A. When opening more than around 50 ports, the system resources might not be
   enough in SCO Open Server and SCO UnixWare.

   The problem can be solved by increasing the maximum number of the system's
   file descriptors. Follow the below steps to rebuild the kernel
   of the Operating System in order to increase the maximum number of
   file descriptors.

   Step 1: Locate the stune file in /etc/conf/cf.d.
        # cd /etc/conf/cf.d
        # ls stune

   Step 2: The stune file contains local system settings for tunable
           parameters. (The parameter settings in the stune file are used
           to override the default values specified in the mtune file.)

           Modify NOFILES parameter of the stune file in SCO Open Server,
           or SFNOLIM parameter of the same file in SCO UnixWare, as shown
           below. This will change the maximum number of file
           descriptors. (Add the parameter by yourself if it is not in
           the stune file.)

           In SCO Open Server:
                NOFILES     xxx

           or, in SCO UnixWare,
                SFNOLIM     xxx

           !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
           Note:
           'xxx' represents the maximum number of file descriptors allowed
           by the Operating Systems. The value of the parameter to be used
           depends on your applications. You should increase the value
           by twice the number of mapping tty ports you intend to
           use, since each mapping tty port consumes two pseudo tty ports:
           master port and slave port. Besides, if your application also
           consumes file descriptors, you should count that number as well.

           For instance, if you want to use 200 mapping ports, NOFILES must
           be set to more than 400 (200 * 2 = 400).

           Furthermore, if you use getty, you must set the value to more
           than 600 (200 * 3 = 600).
           !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

    Step 3: Rebuild the kernel.
        # /etc/conf/bin/idbuild

    Step 4: Reboot the system.
        # reboot
        or
        # shutdown

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