Chapter 30

Chapter 30 Transaction Processing Monitors and Systems

Objectives

To show the design issues in implementing distributed TP systems.
To consider TP case studies in financial applications.

Points to emphasise

The relevance of the issues we have discussed throughout the book to this application area. In particular, the use of: address space, process, thread and IPC mechanisms such as message passing and RPC.
This particular application area has a strong requirement for security.
We have not set up the basis for an in-depth study of security policies and mechanisms. This topic is left for further study on the whole. Aspects that are needed for the development of the material are presented in-line.
Notice the use of batches of transactions.
Notice that there is not a requirement for universal consistency of data replicas at an arbitrarily fine time grain.

Possible difficulties

The first section may look like "more of the same". The change of emphasis is that we are taking a concurrent application and looking at how OS facilities can be exploited.

Lack of knowledge of security issues may prove to be a difficulty.

Personal experience of these systems should offset this.

Teaching hints

Emphasise "what the TP system implementor needs to know about the underlying OS". If you are to buy a TP system to run above your OS you need to know whether they are compatible. It may be that you are intended to buy the hardware and OS as well.
Recall that we discussed the design and checking of capabilities in Chapter 6 and 16. The use of a one-way function was outlined there. We take a similar approach to PIN issuing and validation.
Draw on the students’ experience of ATMs. What services do they offer?
Have cases of fraud been in the news? How was the fraud perpetrated? Is it bank policy to deny internal fraud?