Specifications

14 – Configuring and Monitoring a Redundant Server System
312 R400
When software arbitration is used, terminal servers provide the data link between
the servers and the serial field devices.
The server running as primary communicates with the field devices (via the
terminal servers). If the primary server fails, the backup server becomes the
primary and takes over communications with field devices.
Defining the Arbitration Method
The arbitration method to be used in your redundant server system must be
defined for the primary and backup servers as follows:
1 Specify the arbitration method in a hardware definition file and copy this file
to the primary and backup servers.
2 Run the hdwbld utility on the primary and backup servers to store this
connection definition in the PlantScape database.
While the hdwbld utility is being used to define the arbitration method and to
build the data links, the PlantScape server state must be Database Only.
For information about the content and syntax of hardware definition files and
how to run the hdwbld utility, refer to the Hardware and Point Build Reference.
An example hardware definition file (which you can modify and use) is shipped
with PlantScape. The file is called redun.hdw and is located in \server\user.
Figure 14.4 Software Arbitration
Serial Data
Network
Terminal
Server
Serial Data
Lines
To Seri al
Field Devices
Backup
Server
hsservb
Primary
Server
hsserva
Lines
Terminal
Server
plscpcg.book Page 312 Monday, May 28, 2001 10:11 AM