1. Give a description in your own words of the ACID properties of a transaction.
Atomicity ensures that the transactions done on a database comply to “all or nothing” rule. Rollback of the database is possible when having failure in any part of the transaction.
Consistency refers to the transactions done on a database are operating on a consistent view of the data, before and after they leave the data.
Isolation means all other operations or processes cannot see the completed state or effect of a data during transaction until the transaction is finished.
Durability applies when a transaction is committed; it is guaranteed to persist even in the system failures. Rollback is possible if it is not committed, i.e. not durable.
2. Describe a TP monitor environment. How can a TP monitor stop an operating system being overwhelmed?
(TeleProcessing monitor or Transaction Processingmonitor) is a control program that manages the transfer of data between multiple local and remote terminals and the application programs that serve them. It may also include programs that format the terminal screens and validate the data entered.
In a distributed client/server environment, a TP monitor provides integrity by ensuring that transactions do not get lost or damaged. It may be placed in a separate machine and used to balance the load between clients and various application servers and database servers. It is also used to create a high availability system by switching a failed transaction to another machine. A TP monitor guarantees that all databases are updated from a single transaction. (PC Magazine, 2009)
TP monitor make sure that if the incoming clients requests surpass the number of processes in a server class, the TP monitor dynamically start new ones and this is called Load balancing. Across the computer network the distributing processing and communications activity keep that not even single device is overwhelmed.
References:
PC Magazine, (2009). TP Monitor. Retrieved on May 22nd, 2010 from
http://www.pcmag.com/encyclopedia_term/0,2542,t=TP+monitor&i=53022,00.asp
Wikipedia, LoadBalancing., Retrieved May 22nd, 2010 from,
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