TS/MP Pathsend and Server Programming Manual (G06.24+, H06.03+)

Designing Your Application
NonStop TS/MP Pathsend and Server Programming Manual–132500
2-7
Protecting Transactions
Database Consistency and Concurrency
Potentially, all operations that alter the database are candidates for TMF protection. But
before you can apply TMF protection to your transactions, you need to determine:
•
When to begin a TMF transaction
•
Whether all of the database update operations have to happen together in the same
TMF transaction or whether they can be parts of different transactions
To answer these issues, you have to establish your criteria for database consistency and
decide how much processing concurrency you can achieve in the application. For
example, the Enter Sales transaction affects several pieces of information: order data,
inventory data, shipping data, customer credit, and receivables. Upon examination of this
transaction, you will see that it is possible to make one general assertion about order
processing and about the Enter Sales transaction in particular: An order is not complete
until every piece of information associated with the order is recorded in the \REG,
\CORP, and \WHS databases.
Figure 2-3. Pathway Application Programming for the TMF Subsystem
BEGINTRANSACTION
•
•
•
Request database
services
•
•
Perform checkpointing
as needed
•
•
Abort and restart
transaction if necessary
•
•
ABORTTRANSACTION
or
ENDTRANSACTION
COBOL85, C,
C++, Pascal,
TAL, ...
TRANSID TRANSID
Audited
Database
Files
Requester Server
COBOL85, C,
C++, Pascal, or
TAL
Process request by:
—Reading files
—Locking records
(following TMF
record-locking rules)
—Changing records
in files (changes are
associated with
TRANSID supplied
by requester)
—Aborting transaction
if necessary
•
•
Reply to request
CDT032