Operating Instructions

Chapter 3 – Setting Up the OPC Data Manager
Siemens Building Technologies, Inc. 21
Backup Operation
An OPC Data Manager can be configured in one of three redundancy settings: Primary, Hot, or Warm
backup. Figure 4 shows the connections (lines) and data transmissions (arrows) for each redundancy
setting.
OPC
OPC
ODM ODM
Primary Hot Backup
OPC
OPC
ODM ODM
Primary Warm Backup
Figure 4. Backup Operation.
• A Primary OPC Data Manager operates normally. This setting is used for an OPC Data Manager that
is either a sole OPC Data Manager or the Primary OPC Data Manager of a primary/backup pair.
• A Hot Backup OPC Data Manager operates normally except it does not write to the OPC servers
until the Primary fails. A Hot Backup OPC Data Manager does, however, read from the servers and
thus has up-to-date information on all of the points. Since a Hot Backup OPC Data Manager is active,
the time between failure detection and full operation is minimal, less than a second.
A Hot Backup will stop writing as soon as the Primary’s heartbeat is detected again. This setting is
used to achieve the maximum amount of reliability possible, at the expense of more network traffic
and a higher amount of memory and CPU usage in each OPC server.
• A Warm Backup OPC Data Manager creates groups in each OPC server, but does not activate any
of its groups until the Primary fails. This means that it does not normally read from or write to any of
the OPC servers. Even though a Warm Backup is subscribed, it will likely have bad or outdated
information when it starts up. Because a Warm Backup must activate all of its groups when the
Primary fails, the time needed to respond to the failure may be significant, depending on how many
groups the OPC Data Manager is handling.
A Warm Backup will stop writing to the OPC servers as soon as the Primary’s heartbeat is detected
again, and will need additional time to deactivate all of the groups it has activated. This setting is used
when the amount of additional data traffic generated by a Hot Backup is undesirable, and the
additional time required to enable the groups is acceptable.
Redundancy Display
The current redundancy status is displayed in the status bar of the main window. The left portion of the
status bar changes color and displays a message depending on the redundancy setting and the current
sibling status. Table 2 describes the colors and messages that can be shown.