TMF Introduction (G06.24+)

TMF Overview

HP NonStop Transaction Management Facility (TMF) Introduction—522414-001

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Why Use TMF?

OLTP applications are characterized by concurrent operations on shared data that is

often distributed in a network of systems. They require database consistency, almost

continuous data availability, and very high performance: all provided by TMF.

Each of the following scenarios presents an OLTP problem that can occur, and

discusses TMF solution to that problem.

Point-of-Sale Application Scenario

Problem: Cancelling a Transaction

A clerk using an OLTP point-of-sale application finishes recording 11 pieces of clothing

purchased by customer Smith and submits the charge card number for authorization of

the credit purchase. The reply is negative: “Do not accept the charge.” Assume the

customer has no alternate method of payment.

Solution: Transaction Backout

The clerk has to cancel the transaction. Because this is an OLTP application, all the

purchases were recorded as they were entered; now they must be undone. Using

transaction backout, TMF undoes all the individual sales in the transaction.

In this point-of-sale application, TMF ensures all operations in the transaction are

undone, so the database remains consistent. The clerk simply needs to cancel the

transaction.

Financial Application Scenario

Problem: Node Failure

A broker enters a transaction to sell 200 shares of stock just as the node in which the

server executing the transaction on the database fails.

Solution: Transaction Backout

TMF detects the failure and backs out the transaction. The broker’s program

determines that the transaction has failed and automatically restarts it. This second

attempt is successful.

In this stock transaction, TMF protects the transaction by ensuring that it completes as

a unit. TMF also keeps the database consistent despite the failure of a major

component, the node. The broker notices none of these problems because the

submitted transaction completes quickly.