Introduction to Data Management

Ensuring Database Consistency With TMF

15873 Tandem Computers Incorporated 7-11

Figure 7-7. TMF Record Locking

S8020-02

Transaction 1

Transaction 2

Transaction 3

Server

Disk

Process

Audited

Files

Records locked

for Transaction 1

until it commits

or aborts

Record locking gives TMF a stable image of each affected record prior to and after the

transaction. Record locking allows TMF to undo and redo database changes made by

a transaction, with the guarantee that no other transaction could have altered the same

records while this transaction was in progress.

Relationship to Other

Products

In PATHWAY applications, you normally request TMF operations by coding SCREEN

COBOL statements in your screen programs. As a result, TMF performs all the

required auditing and transaction backout functions for your application

automatically.

TMF complements the PATHWAY transaction processing system and the NonStop

SQL database management system. Use of these three products together provides

maximum performance, data integrity and consistency, and programmer productivity

for your applications.

As noted earlier, the services of TMF are available through PATHMAKER.

Furthermore, TMF is not restricted to PATHWAY applications: statements that access

TMF are available in most other compiled and interpreted languages supported by

Tandem.