IDEC WindSRV - Manual (Page 58)

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1. Write all values for all tags
'Write all values for all tags' forces the server to attempt to Write every value to the controller. In this mode, the server
continues to gather OPC Write requests and add them to the server's internal Write queue. Then, the server processes
the Write queue and attempts to empty it by writing data to the device as quickly as possible. This mode ensures that
everything written from the OPC client applications will be sent to the target device. This mode should be selected if the
Write operations's order or the Write item's content must uniquely be seen at the target device. This is the default
mode.
2. Write only latest value for non-Boolean tags
Many consecutive Writes to the same value can accumulate in the Write queue, due to the time required to actually
send the data to the device. If the server were to update a Write value that has already been placed in the Write queue,
far fewer Writes would need to be done to reach the same final output value. In this way, no extra Writes accumulate in
the server's queue. When the user stops moving the slide switch, the value in the device is at the correct value at
virtually the same time. This is the mode of operation that the second Write optimization mode, 'Write only latest value
for non-Boolean tags,' allows. As the mode states, any value that is not a Boolean value will be updated in the server's
internal Write queue and will then be sent to the device at the next possible opportunity. This can greatly improve the
application's overall performance.
Note: 'Write only latest value for non-Boolean tags' does not attempt to optimize Writes to Boolean values. This allows
users to optimize the operation of HMI data (such as the slide switch example) without causing problems with Boolean
operations like a momentary push button.
3. Write only the latest value for all tags
'Write only the latest value for all tags' takes the theory behind the second optimization mode and applies it to all tags.
It is especially useful if the application only needs to send the latest value to the device. This mode optimizes all Writes
by updating the tags currently in the Write queue before they are sent.
Duty Cycle
The Duty Cycle selection is used to control the ratio of Write operations to Read operations. The ratio is always based
on one Read for every one to ten Writes. The duty cycle is set to ten by default, meaning that ten Writes will occur for
each Read operation. Although the application is doing a large number of continuous Writes, it must be ensured that
Read data is still given time to process. A setting of one will result in one Read operation for every Write operation. If
there are no Write operations to perform, Reads will be processed continuously.
Note: We strongly suggest that the application be characterized for compatibility with these Write optimization