Emerson Exchange 365

I wanted to share an application from pretty interesting project that one of our engineering teams had recently.  They needed to pull in 300,000 data values (not a typo) into their DeltaV Operate interface from their Siemens PCS7 system.  The standard way of doing that would mean at least 10 application stations with OPC interfaces to the old system - not to mention the risks of overloading the connections, etc.  The team was able to develop a custom solution that solved this customers problems.  Since the data didn't need to be historized on the DeltaV side, they could bring the values into the operator interface on demand.  They created a custom VBA application that pulled the data directly into the operator interface (with some help from an OPC tunneler).  Since only the currently viewed tags were being pulled across the interface, the customer didn't have to invest in dozens of servers or lots of licenses.  This was the critical step in enabling a phased migration of the PCS7 system to DeltaV - the operators could use new DeltaV graphics and see the values from their old system while the I/O is gradually cut over between the systems.

Have any of you attempted a horizontally-phased migration strategy, or have you had a need to interface large amounts of data or to interface with a PCS7 system?  Some approach similar to this one might work for you.  I'd be interested to hear any stories.