In certain cases, it is possible for the communications driver to read data from the I/O device at a greater rate than the application is able to send the data out to client machines through the RPC link. By default, data RPC packets will not be queued up by VTS. If a data packet for a particular address is already on the RPC outbound queue and a new data packet for the same address is placed on the queue, it will replace the original data packet. The result is that there will never be more than a single data packet for a particular address on the outbound queue at any given moment. This has a side effect that some data packets may not be seen by the clients.
Driver tags may have an optional variable named CoalesceRPC, defined within the main module of the driver tag. All data packets will be transmitted to the clients through RPC if this variable is set to non-zero, i.e. all packets will be queued and delivery to clients is guaranteed. This mode has a possible side effect of overflowing the RPC outbound queue should the data collection rate be greater than the network speed.