Specifications

Point Servers
PlantScape Server and Client Configuration Guide 119
Point Servers
A point server is a software component that interfaces between a PlantScape
Server and devices and channels that are represented in PlantScape as flexible
points.
This section discusses configuration issues in PlantScape that apply to any point
server. For information about a particular point server, see the documentation
supplied with the field devices represented within it.
The point server is responsible for servicing requests from PlantScape for named
point parameter data (data that is referenced with ASCII names) and for
notifications (alarms, events, messages and delays). The point server maps these
requests to a device-specific protocol and communicates with individual devices
to satisfy the requests.
You can run a point server on the same computer as the PlantScape Server, or on
a separate computer. You can run more than one point server on a computer, but
each point server communicates with only one PlantScape Server.
Point servers read data directly from the field. The value of a flexible point is not
stored in the server unless the point is configured in history collection. When a
display containing the flexible point is called up, the server creates the point if it
does not already exist. The point’s parameter values are read from the field via
the point server, and then shown on the display. Parameter values are updated
and cached by the server for a configurable period after a point is accessed, so
that the next time is accessed the updated value is immediately available.
Flexible points can be added to groups, trends, point control schedules, reports,
and displays.
Considerations
• Flexible points do not support algorithms. A derived server database point
must be used whenever a server algorithm is required to be configured on a
flexible point parameter.
• Flexible points are not processed by the PlantScape Server’s alarm
subsystem. For most point servers this is not an issue, because the controller
or point server generates alarms on the point. However, if you are using a
point server interface that does not support alarming, you must use derived
server database points to do the alarming. See the reference for the
particular point server for more information.
• If you are using point servers, you need to enable areas on your system.
plscpcg.book Page 119 Monday, May 28, 2001 10:11 AM