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Optimizing Server Performance
Server Operational Parameters
76 • • • • Chapter Six - Advanced Options
Networks vary widely from one to another. Every network has different devices,
different numbers of RS-485 ports to support, a different number of devices, and
various client software requesting different amounts of data. System administrators
with Modbus RTU network experience may be able to analyze their particular
network's needs and adjust some of the PMCS DDE Server's advanced settings to
improve its performance. These settings are discussed below.
Clicking on this button in the Configuration dialog box causes the Server
Operational Parameters dialog box to appear:
Protocol Timer Tick
The Protocol Timer Tick is the time interval (in milliseconds) at which protocol is
executed; the frequency at which the Server checks for work to do. A good analogy
might be that the protocol timer tick serves as a metronome or heartbeat to the
Server. Every tick, the Server executes a function, whether it is to listen at a
particular port or to send a message to a device. The default is 65 milliseconds. At
values below this level, the Server may query devices too quickly for the devices to
consistently answer correctly.
The Protocol Timer Tick is the resolution of the scan interval – increasing this value
slows down the Server but may improve communication reliability. Decreasing this
value reduces communication reliability but may slightly speed up data-refresh rates.
If you are not sure how to adjust this value for your network, leave it set at 65 msec.
NOTE: 10 msec is the minimum value for this setting.
Valid Data Time-out
A client application sends a request for data to the PMCS DDE Server. The Valid
Data Time-out is the time (in milliseconds) that elapses before a time-out error
message is sent to the client that requested the data. The default number in this field
is 5000 (5 seconds). If no reply is sent from the Server to the client in this length of
time, a time-out error message is sent instead.
DDE Server User's Guide
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