HP NonStop G-Series User Manual
Page 22
Client Programming
Introduction to the Tandem DDE Gateway
1–10
110838 Tandem Computers Incorporated
the Bridge program. You can configure a memory cache on the workstation for the
data dictionary to ensure good performance.
Element-by-Element DDE Communication
To explain the element-by-element approach, the client application steps necessary to
perform the transaction to retrieve employee data (described above in SCOBOL) are
shown in Figure 1-4.
Figure 1-4. Element-by-Element DDE Communication
Initiate (TDMGW , PATHWAY)
Execute ([BEGINTRANSACTION])
Poke (EMPLOYEE-NUMBER, CF_TEXT, Employee no.)
Execute ([SEND])
Request (REPLY-CODE, CF_TEXT)
Data (Value of REPLY-CODE)
Execute ([ENDTRANSACTION])
Terminate
Execute ([INITIALIZESERVICE(READ-EMPLOYEE)]
Request (LAST-NAME, CF_TEXT)
Data (Value of LAST-NAME)
Client
Application
(Element-
by-
Element)
Tandem
DDE
Gateway
(Message
Layouts
and Data
Conversion
in Tandem
DDE
Gateway)
004
1.
Use the DDE Initiate function to start a DDE conversation with the Tandem DDE
Gateway. Use the application name TDMGW and the DDE topic name
PATHWAY.
2.
Use the DDE Execute function to tell the Tandem DDE Gateway the transaction
type. Use the command [INITIALIZESERVICE(READ-EMPLOYEE)]. The
transaction name READ-EMPLOYEE is configured in the Tandem DDE Gateway
as a ServiceName object and cross-referenced there to a Pathway server class.
3.
Use the DDE Execute function to tell the Tandem DDE Gateway to start a Tandem
Transaction Monitoring Facility (TMF) transaction. Use the command
[BEGINTRANSACTION]. (This step is not really needed for this read-only
transaction; it is used only to illustrate the procedure.)
4.
Use the DDE Poke function to pass the value of the EMPLOYEE-NUMBER data
element of the READ-REQUEST-MESSAGE to the Tandem DDE Gateway. You
refer to the EMPLOYEE-NUMBER data element in the DDE Poke function by its
fully qualified name of READ-REQUEST-MESSAGE. EMPLOYEE-NUMBER (the
fully qualified data element names are not shown above due to a lack of space).