sac(1M)                          DG/UX R4.11                         sac(1M)


NAME
       sac - service access controller

SYNOPSIS
       sac -t sanity_interval

DESCRIPTION
       The Service Access Controller (SAC) is the overseer of the server
       machine.  It is started when the server machine enters multiuser
       mode.  The SAC performs several important functions as explained
       below.

       Customizing the SAC environment.  When sac is invoked, it first looks
       for the per-system configuration script /etc/saf/_sysconfig.  sac
       interprets _sysconfig to customize its own environment.  The
       modifications made to the SAC environment by _sysconfig are inherited
       by all the children of the SAC.  This inherited environment may be
       modified by the children.

       Starting port monitors.  After it has interpreted the _sysconfig
       file, the sac reads its administrative file /etc/saf/_sactab.
       _sactab specifies which port monitors are to be started.  For each
       port monitor to be started, sac forks a child [fork(2)] and creates a
       utmp entry with the type field set to LOGIN_PROCESS.  Each child then
       interprets its per-port monitor configuration script
       /etc/saf/pmtag/_config, if the file exists.  These modifications to
       the environment affect the port monitor and will be inherited by all
       its children.  Finally, the child process execs the port monitor,
       using the command found in the _sactab entry.  (See sacadm; this is
       the command given with the -c option when the port monitor is added
       to the system.)

       Polling port monitors to detect failure.  The -t option sets the
       frequency with which sac polls the port monitors on the system.  This
       time may also be thought of as half of the maximum latency required
       to detect that a port monitor has failed and that recovery action is
       necessary.

       Administrative functions.  The Service Access Controller represents
       the administrative point of control for port monitors.  Its
       administrative tasks are explained below.
       When queried (sacadm with either -l or -L), the Service Access
       Controller returns the status of the port monitors specified, which
       sacadm prints on the standard output.  A port monitor may be in one
       of six states:

       ENABLED   The port monitor is currently running and is accepting
                 connections.  See sacadm(1M) with the -e option.

       DISABLED  The port monitor is currently running and is not accepting
                 connections.  See sacadm with the -d option, and see
                 NOTRUNNING, below.

       STARTING  The port monitor is in the process of starting up.
                 STARTING is an intermediate state on the way to ENABLED or
                 DISABLED.

       FAILED    The port monitor was unable to start and remain running.

       STOPPING  The port monitor has been manually terminated but has not
                 completed its shutdown procedure.  STOPPING is an
                 intermediate state on the way to NOTRUNNING.

       NOTRUNNING
                 The port monitor is not currently running.  (See sacadm
                 with -k.)  This is the normal ``not running'' state.  When
                 a port monitor is killed, all ports it was monitoring are
                 inaccessible.  It is not possible for an external user to
                 tell whether a port is not being monitored or the system is
                 down.  If the port monitor is not killed but is in the
                 DISABLED state, it may be possible (depending on the port
                 monitor being used) to write a message on the inaccessible
                 port telling the user who is trying to access the port that
                 it is disabled.  This is the advantage of having a DISABLED
                 state as well as the NOTRUNNING state.

       When a port monitor terminates, the SAC removes the utmp entry for
       that port monitor.

       The SAC receives all requests to enable, disable, start, or stop port
       monitors and takes the appropriate action.

       The SAC is responsible for restarting port monitors that terminate.
       Whether or not the SAC will restart a given port monitor depends on
       two things:

              ·  the restart count specified for the port monitor when the
                 port monitor was added by sacadm; this information is
                 included in /etc/saf/pmtag/_sactab

              ·  the number of times the port monitor has already been
                 restarted

FILES
       /etc/saf/_sactab
       /etc/saf/_sysconfig
       /var/adm/utmp
       /var/saf/_log

SEE ALSO
       sacadm(1M), pmadm(1M).


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