HP NonStop G-Series - Manual (Page 60)

DDE Functions
Creating Client Applications
4–4 110838 Tandem Computers Incorporated
DDE Functions You can use five different DDE functions to communicate with the Tandem DDE
Gateway from your client application, including the following:
DDE Initiate, which starts a DDE conversation.
DDE Terminate , which ends a DDE conversation.
DDE Execute , which causes the Tandem DDE Gateway to execute the provided
command. This command, for example, could start a TMF (Transaction
Monitoring Facility) transaction or send a message to a Tandem server.
DDE Poke , which sends data to the Tandem DDE Gateway to be put in a buffer
that will subsequently be sent to a Tandem server.
DDE Request , which retrieves data from a buffer in the Tandem DDE Gateway
containing a reply message from a Tandem server.
Each of these functions is described in detail in the following paragraphs.
Caution The verbs used in this manual for DDE functions are the same as those used in Microsoft Excel.
Although the DDE protocol is standard, the verbs used in the client tools are not. You should review the
descriptions of the DDE verbs for a given tool and match them to the verbs used in this manual.
See Table 1-1 for examples of DDE verbs used in different applications. See the \EXAMPLES
subdirectory for examples of different tools.
DDE Initiate Function The DDE Initiate function starts a DDE conversation between a client application and
the Tandem DDE Gateway. Use the DDE Initiate function with the DDE application
name of TDMGW and a DDE topic name of PATHWAY or SERVER to start a DDE
conversation with the gateway.
Syntax
INITIATE (TDMGW, SERVER) or
INITIATE (TDMGW, PATHWAY)
The two forms have identical meaning to the Tandem DDE Gateway. The variants
are for readability of client applications only.
You should keep DDE conversations as short as possible. To initiate and terminate a
DDE conversation uses very few workstation resources, and causes no data
communications traffic. When you start a DDE conversation and issue the first DDE
Execute INITIALIZESERVICE command, data communications resources are allocated
temporarily by the Tandem DDE Gateway to your client application. Therefore, these
data communications resources are temporarily denied to other client applications on
the workstation.
A good duration for the DDE conversation is the time it takes the Tandem system to
process the function related to one button in the client application (such as an OK
button to retrieve employee information). The Tandem interaction may consist of
many communications with one or more Tandem servers, but there should generally