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 (see 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:
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:
Created by unroff & hp-tools. © by Hans-Peter Bischof. All Rights Reserved (1997).
Last modified 21/April/97