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

Writing Pathway Servers
NonStop TS/MP Pathsend and Server Programming Manual–132500
4-9
Grouping Transaction Operations
Example 1
Some logical transactions do not have to be identified as TMF transactions. For
example, a logical transaction locates a single record and displays the record contents.
Because this transaction changes nothing in the database, it does not affect consistency
and does not have to be a TMF transaction.
Example 2
A data-entry transaction with a group of accesses that insert new data into the database
should be a TMF transaction. For example, a logical transaction records receipt of some
items for a stockroom by accepting the stock codes and quantity received from a data-
entry operator and then updates the records (in an audited file) for the items.
Because the first guideline applies, you should arrange to begin a TMF transaction after
the data is accepted and to end the transaction after the last record is updated. The TMF
subsystem ensures that all changes resulting from the one operator entry either are
permanent or are backed out in case the transaction aborts. Note that because any change
to an audited file requires a transaction identifier, this example is also true if the
transaction inserts only one record in the file.
Example 3
An update transaction should be a TMF transaction. For example, assume a logical
transaction does the following:
1. Accepts a specification from the operator
2. Performs the equivalent of an inquiry operation to find the data that will be updated
3. Releases the locks obtained for the inquiry
4. Displays the data for the operator
5. Accepts modifications to the displayed data (saving a copy of the original displayed
data)
6. Performs the inquiry a second time
7. Verifies that the results of the first inquiry and the second inquiry are the same
8. Writes the modified record to the database
The transaction should be implemented as two TMF transactions. The first should begin
after the data is accepted and should end (rather than release the locks) after the last
record is read. The second should begin after the modifications to the displayed data
have been accepted and should end after the last modified record is written to the
database. If the inquiry part of the transaction is just a single read, however, there is no
need for the first inquiry to be part of a TMF transaction.