TMF Introduction (G06.26+)

TMF Application Programming
HP NonStop TMF Introduction—522414-002
5-13
Developing Servers for Database Access
If a transaction requires only one screen display (allowing the terminal operator to
enter all the required data at once), the transaction design is straightforward and the
three preceding questions do not apply.
If, however, the transaction requires two or more screen displays to accumulate its
data, one of the following two possible designs can be considered:
•
A single, long TMF transaction
•
A context-saving TMF transaction
Long Transactions
A long transaction is one in which a requester accepts data and sends it to servers
several times in a single TMF transaction. This design uses the TCP’s ability to
provide transaction restart if a TMF transaction is interrupted; however, it precludes a
requester issuing a CHECKPOINT statement to ensure recovery of accepted operator
input data (checkpoints are not allowed within a TMF transaction).
Figure 5-4. Mixed Database Access by an HP COBOL Server
Procedure Division.
...
200-Access-SQL-DB.
*With SQL statements.
...
400-Access-ENSCRIBE-DB.
*With HP COBOL statements.
READ ...
...
NonStop
SQL
Database
Enscribe
Database
Requester
VST027.vsd
EXEC SQL
FETCH...
HP
COBOL
Server