Concurrency Control Case Study

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Problems may also occur with the locking mechanism within concurrency control, two examples of such problems are:
Deadlock can be the first of two problems which may occur, the second problem that may occur is live lock
a. Deadlock
When two resources are looking to be unlocked at the same time, however this cannot happen so it is necessary for them to wait for each other. If two or more processors are waiting for an item to be unlocked they are waiting in a circulating chain. This means that when they eventually become available they will unlock and the process can be completed.
Deadlock is very common and may occur during the processing of many items, it is most likely to happen when processors are waiting to see a specific type of exclusive resources. A very good example of this would be “Some computers, usually those intended for the time-sharing and/or real-time markets, are often equipped with a hardware lock, or hard lock, which guarantees exclusive access to processes, forcing serialization” Dead Lock, Introduction to Concurrency Control, 2006 .
A simple way to think of deadlock is to say that if the actions of two people cannot be satisfied a deadlock situation has basically occurred
b. Live lock.
This is very similar to deadlock however there is constantly change is happening with the processors however there is no progression on to the next stage of the process.
An example of how a live lock situation occurs is as follows:
“when numerous people arrive at a four way stop, and are not quite sure who should proceed next. If no one makes a solid decision to go, and all the cars just keep creeping into the intersection afraid that someone else will possibly hit them, then a kind of livelock can happen.”
c. basic time stampin...

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...s to happen and also it will give the user a trouble-shooter guide to facilitate the and help them to understand and assist the programme during its main task. This trouble-shooter feature has been included with the most recent versions of the Microsoft SQL database package.
Concurrency within an Oracle database
If there was a single user database the user can modify the data in the database without concern for other users modifying or changing the same data at the same time however the statements we have multiple simultaneous transactions can be obtained with all of the one time.
Within the Oracle database control of data concurrency and consistency is vital because it may be a multiuser environment.
Database researchers have defined serializability as a process which gives transactions behaviour which makes them appear as if they are all happening at the one time.

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