OFSOPC Driver Parameters

OFSOPC Driver Version

Use the latest version of OFSOPC that is available. This document targets OFSOPC 1.2.x, or greater.

Group Management

The OFSOPC driver defines 3 groups per PLC. These groups are polled at a rate defined by the Group<i>UpdateRate parameter in citect.ini. Set these poll rates such that:

• Group1UpdateRate < Group2UpdateRate < Group3UpdateRate

• Group1UpdateRate < Alarm scan Time

• Group2UpdateRate <Trend sampling Time

The "Group Minimum Update rate" is different for each of these groups and can be set using OFS parameters.

The default values are:

Group1UpdateRate = 400 ms

Group2UpdateRate = 1000 ms

Group3UpdateRate = 3000 ms

Each requested tag will be activated in the group which provides the lowest (e.g. fastest) update rate that is faster than the requested rate. For example, a tag with a requested rate of 2s will be activated in Group 2 if the default values are being used.

If no group provides such a rate then the fastest one is used. For example tags requested at 200 ms with default configuration will be put in 400 ms group.

Usually Group 1 (the fastest group) is associated with tags in the active page and alarms. The Group 2 should be targeted for trends and the group 3 is mostly there for slow trends if they are configured.

With the default Plant SCADA configuration, the Group1 (400 ms) will contain alarms ([Alarm] ScanTime =500ms) and page items ([Page] ScanTime =250ms).

See Group Management Parameters.

Logging

The OFSOPC driver can log combinations of trace levels across different categories. This is achieved by setting the following Citect.ini parameters:

[OFSOPC]DebugLevel

[OFSOPC]DebugCategory

These settings have an impact on the performance of the driver and therefore it is recommended to switch them off by removing these parameters from the citect.ini file to get optimal performance.

See Logging Parameters.

MaxPending

This parameter defines the maximum number of pending commands that the OFSOPC driver holds for immediate execution. The default value is now 1200. If this value exists in Citect.ini, it should be updated (or removed to take into account this new default value).

This parameter is common to other drivers it is defined under [OPC] and not [OFSOPC] section in the Citect.ini file.

Summary of recommended OFSOPC Configuration parameters

In summary, the recommended driver parameters settings for optimal performance are as follows: