September 2010
Intermediate to advanced
1704 pages
111h 8m
English
Isolation levels determine the extent to which data being accessed or modified in one transaction is protected from changes to the data by other transactions. In theory, each transaction should be fully isolated from other transactions. However, in practice, for practical and performance reasons, this might not always be the case. In a concurrent environment in the absence of locking and isolation, the following four scenarios can happen:
• Lost update—In this scenario, no isolation is provided to a transaction from other transactions. Multiple transactions can read the same copy of data and modify it. The last transaction to modify the data set prevails, and the changes by all other transactions are ...