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The PICS real time database agent, RTDBA replaced both RTDB and RTRemote in PICS III. RTDBA is responsible for distribution of real time data throughout the PICS network (via UDP broadcast messages). RTDBA also distributes real time data to client applications in the same machine using EVI's IPCAPI. Incoming data received through the IPCAPI is broadcast (from the PRIMARY side only) so that all nodes may see it. Incoming data received through UDP broadcasts are distributed to local applications as necessary. RTDBA runs on ALL systems on the PICS display network (WAN customers still use RTClient) .
RTDB and RTRemote became obsolete in PICS III and were both replaced with RTDBA.
The master of all PICS real time databases, RTDB is responsible for primary distribution of real time data throughout the PICS network (via UDP broadcast messages to RTRemotes). RTDB also distributes real time data to client applications in the same machine using EVI's IPCAPI. Incoming data is received both through the IPCAPI and UDP broadcasts from RTRemote nodes. Only one subsystem may run RTDB (but it may run on both the primary and backup node, when available).
A near duplicate to RTDB, RTRemote runs on all PICS subsystems except for the one running RTDB itself. RTRemote listens to the UDP data stream and distributes real time data to local client applications. RTRemote can also receive new data into the real time system through the IPCAPI, and when it does that data is sent (via UDP) to RTDB for distribution. RTRemote will only distribute data that it receives from RTDB via UDP to local clients.
For end-user nodes, typically running somewhere across a wide-area network from PICS, RTServer provides a TCP-based data stream. Where a UDP broadcast is stopped at the first gateway/bridge in a network, TCP may travel across many hops. Unfortunately, TCP is a conversation between two (and only two) parties, so each and every end-user node requires its own TCP data stream. Because of the potential for bandwidth consumption, RTServer only transmits the PICS Time point, plus any points specifically requested by the end-user node across the TCP channel. Running applications such as RtdbDDE or Monitor at an end-user station requires that ALL points available be shipped, greatly increasing the bandwidth required.
This is the client end of an RTServer connection. It distributes PICS real time data to local client applications. RTClient has a facility for specifing the data reporting rate that should be used by any end-user that does not require high-speed data. Lowering the reporting rate can significantly decrease the bandwidth required by end-user nodes.
The PICS Real Time DDE (Dynamic Data Exchange) interface allows any 3rd party application that implements the standard DDE protocol to access PICS real time data.
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