Exercise 11: TP monitors and transaction protocols

1. Give a description in your own words of the ACID properties of a transaction.

In computer science, ACID (atomicity, consistency, isolation, durability) is a set of properties that guarantee database transactions are processed reliably. The concept of ACID is to evaluate databases and application architecture. In the context of databases, a single logical operation on the data is called a transaction. For example, a transfer of funds from one bank account to another, even though that might involve multiple changes (such as debiting one account and crediting another), is a single transaction.

2. Describe a TP monitor environment. How can a TP monitor stop an operating system being overwhelmed?

TP monitor, short for transaction processing monitor, a program that monitors a transaction as it passes from one stage in a process to another. The TP monitor's purpose is to ensure that the transaction processes completely or, if an error occurs, to take appropriate actions.
TP monitors are especially important in three-tier architectures that employ load balancing because a transaction may be forwarded to any of several servers. In fact, many TP monitors handle all the load balancing operations, forwarding transactions to different servers based on their availability.



Reference

Wikipedia. (2010). ACID. Retrieved at 28 Apr, 2010, from http://en.wikipedia.org/wiki/ACID

Webopedia. (2010). TP monitor. Retrieved at 28 Apr, 2010, from http://www.webopedia.com/TERM/T/TP_monitor.html