HP NonStop G-Series - Manual (Page 76)

Application Design Considerations
Creating Client Applications
4–20 110838 Tandem Computers Incorporated
large number of DDE Request functions could be required to transfer the details for all
guests within the message to storage in the client application.
Consider the alternatives listed below when dealing with large tables in messages to
ensure good client application performance.
Use DDE Poke or DDE Request functions against whole rows of the table
(containing a number of data elements). Use the group name for the row in the
DDE function. The data will be treated by the Tandem DDE Gateway as one
alphanumeric data element. You must perform any necessary data conversions
for individual data elements with client application code. See Section 6, “Data
Conversion,” for more details.
This alternative might not be appropriate if there are data elements that contain
binary data (such as integers) in the row of the table. See the “DDE Poke and DDE
Request of Group Data Elements” topic above.
Consider whether all data in the table needs to be transferred between the
Gateway and the client application in one burst of processing. An alternative is to
trickle the data between the Gateway and the client application in response to the
client application user’s actions. This can also reduce memory requirements in the
client application.
Use the Tandem DDE Gateway binary-pass-through communication approach.
Also, remember that you can use both the element-by-element and binary-pass-
though communication approaches to access the same message data within one
DDE conversation.
Use your client development tool’s string concatenation operator to construct
subscripted data element names. If your client tool has a string concatenation
operator, it should not be necessary to code one DDE Poke or DDE Request for each
subscript value. Use a loop and construct data element names with subscripts within
the loop. For example, where + represents a string concatenation operator:
For Index = 1 To 10
ElementName = "READ-REPLY.SALARY(" + Index + ")"
REQUEST (ElementName) , into TableVariable (Index)
Next Index
Note This code is for illustration purposes only - it is not from any particular client application development tool.
Alphanumeric Data
Elements Containing
Special Characters
Alphanumeric data items can contain special characters that have meaning to the
Tandem DDE Gateway when the CF_TEXT format is being used. The special
characters are binary zeros (decimal 0), carriage return (decimal 13), and line feed
(decimal 10). An example of an alphanumeric data item that might contain special
characters is a Guardian timestamp.
If your application needs to DDE Poke and DDE Request this type of data, then you
have a number of alternatives.
Using DDL on the Tandem system, redefine the binary data element as a table of
binary numbers. Then use DDE Poke and DDE Request functions against the table
elements.