TMF Introduction (G06.26+)

TMF Application Programming
HP NonStop TMF Introduction—522414-002
5-15
Developing Servers for Database Access
Disadvantages of long transactions are:
•
Resources could be locked for an indeterminate amount of time. Locking
resources for seconds or minutes might be acceptable; locking resources for hours
is not acceptable. An application should ensure that an operator cannot leave to
perform some other task before finishing a transaction so that locked resources
can be released.
•
Transaction restart requires the operator to reenter input.
Context-Saving Transactions
A context-saving transaction is one in which a requester accepts and collects all
operator input before starting the TMF transaction and sending a database update
request to a server. A typical sequence of SCREEN COBOL actions for context-saving
transactions is shown in Figure 5-6.
Figure 5-6. A Context-Saving Transaction
VST030.vsd
Server
Database
Transaction State
Requester
ACCEPT data
Save data in
TCP's terminal
context area.
•
•
•
ACCEPT data
Save data in
TCP's terminal
context area.
•
•
•
ACCEPT data
BEGIN-TRANSACTION
SEND to server
SEND to server
END-TRANSACTION
Display 1
Operator
Action
Display 2
Display 3
Operator
Action
Operator
Action