Specifications

Defining the Redundant Connections
PlantScape Server and Client Configuration Guide 311
Defining the Redundant Connections
Details about the connection between the two servers in a redundant server
system are defined using entries in a hardware definition file. The following
details need to be specified for the connection:
• The Redundant Arbitration method (see the description of Redundant
Arbitration below)
• The data links between the primary and the backup servers
To define the redundant connections in the server database, you need to create
entries in a hardware definition file and then run the hdwbld utility to define the
details in the server database.
Redundant Arbitration
Redundant arbitration is the task of deciding which of the servers will run as the
primary (that is, communicating with field devices and Stations) and which will
run as the backup (providing a standby system in case the primary fails).
The method of arbitration is called Software arbitration.
Software Arbitration
When software arbitration is used, software running on the primary and backup
servers provides the arbitration. Each server polls the other (via the network) so
that it knows if the other server has failed.
For example, if hsserva is running as the primary server and fails, the arbitration
software running on hsservb detects this and switches from running as backup to
running as primary.
Figure 14.4, “Software Arbitration” on page 312 illustrates software arbitration.
plscpcg.book Page 311 Monday, May 28, 2001 10:11 AM