Multiplexing and Redundancy

[T@TPCG]

I have a Lookout 6.1 client/server application that multiplexes data for 150 wastewater lift stations on to a

single panel from a DataTable object. I have a redundant server that starts an identical standby server process

in the event the primary server fails. There are 10 duplicate remote client processes that also use multiplexed

DDE enabled DataTable objects.

In a failover scenario, the remote clients' TCP/IP connections all work properly with dynamic symbolic links;

But, none of the clients' DataTable objects will connect to the standby computer because the client DataTables'

DDE Service parameter does not resolve a symbolic link and is static to the primary computer, which is offline

during failover.

Although this client program structure worked in Lookout prior to 4.0 using NetDDE redundancy, the new

methodology makes multiplexing DDE enabled DataTables in client processes impossible for a client/server

architecture needing redundancy, because the client DataTables' DDE service parameter remains static in failover.

Is there a way to redirect the clients' Datatable DDE service parameter to the standby computer in Lookout 6.1

another way, so I can still use the DDE enabled DataTable multiplexing method on the existing clients in a

failover?

DataTable configuration example:
Service: \\PRIMARY\NETDDE$  <**Static, will not resolve a symbolic link to \\STANDBY\NETDDE$
Topic: SERVERPROCESS$
Item: TestDataTable

Terry Parks, Engineering Analyst
Terrebonne Parish Consolidated Government(TPCG)
Utilities - Pollution Control

[Mike@DTSI]

Good question, i would like to know myself.

We usually have a single symbolic link and connect the objects directly, no need for a datatable.

Looking forward to an answer

Mike

[Ryan.S]

Yes, usually I just create a symbolic link and connect object. That's really a problem if you want to dynamicly connect datatable to dde server. The parameters of datatable are all text constant.

Till now, I can't find a way.

[T@TPCG]

The following statment is taken directly from Chapter 14 'Setting Up Redundancy' of the

Lookout Developer's manual(pg 14-1).

"If your client process uses NetDDE in shifting access from one computer to another, it

will work in the current version of Lookout."

This statement, coupled with the notion of backward compatibility, brings me to the

question; Could this be considered a bug or anomaly in Lookout eligible for a fix?

Terry

[Mike@DTSI]

Updating the DataTable CBX would allow using an expression to create a dynamic link.... NI Lookout team, please?

Mike

[T@TPCG]

Earlier I misstated that this was impossible; But, the alternative is to symbolically link each cell of the

clients' local datatable to each cell of the servers' local data table, in my case, thousands of

connections. This nullifies the programming simplicity of exchanging a large quantity of data through DDE

enabled datatables between remote processes. The up side is that TCP/IP is more stable than DDE.

Terry