Exercise 11

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

ACID refers to Atomicity, Consistency, Isolation and Durability (Wikipedia, 2010).

For a transaction to have ACID properties, the database can only be updated if the whole transaction is finished. If part of the transaction is finish but not all, the whole update data should be dropped and the database should keep unchanged. In addition, the transaction data format should follow the database schema data format, such action will ensure the data get updated into the database. Moreover, the transaction should not access the data being updated by other process, it should wait until the data is released by the other transaction. Finally, when the transaction is success completed, the data should be updated into the database accordingly. Data could be roll back from the database even after system failure.

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

A Transaction Processing (TP) monitor environment is that a control program will manages the transfer of data between multiple local and remote terminals and the application program that serve them.

For a distributed Client/Server, a TP monitor will ensures the transactions never get lost or damaged. It can be a placed in a separate workstation and used to balance the load between various application servers, Database servers and clients. Moreover, it creates a high availability system by fail over the transaction to a good machine. Finally, it guarantees that all databases are only be updated by a single transaction (Pcmag, 2010)