70-516 Question #56: Real Exam Question with Answer & Explanation

The correct answer is A. ReadUncommitted. Unspecified A different isolation level than the one specified is being used, but the level cannot be When using OdbcTransaction, if you do not set IsolationLevel or you set IsolationLevel to Unspecified, the transaction executes according to the isolation level that is determine

Question

You use Microsoft Visual Studio 2010 and Microsoft .NET Framework 4.0 to develop an application that connects to a Microsoft SQL Server 2008 database. The application performs a database query within a transaction. You need to ensure that the application can read data that has not yet beed commited by other transactions. Which IsolationLevel should you use?

Options

AReadUncommitted
BReadCommitted
CRepeatableRead
DUnspecified

Explanation

Unspecified A different isolation level than the one specified is being used, but the level cannot be When using OdbcTransaction, if you do not set IsolationLevel or you set IsolationLevel to Unspecified, the transaction executes according to the isolation level that is determined by the driver that is being used. Chaos The pending changes from more highly isolated transactions cannot be overwritten. ReadUncommitted A dirty read is possible, meaning that no shared locks are issued and no exclusive locks are honored. ReadCommitted Shared locks are held while the data is being read to avoid dirty reads, but the data can be changed before the end of the transaction, resulting in non-repeatable reads or RepeatableRead Locks are placed on all data that is used in a query, preventing other users from updating the data. Prevents non-repeatable reads but phantom rows are still possible. Serializable A range lock is placed on the DataSet, preventing other users from updating or inserting rows into the dataset until the transaction is complete. Snapshot Reduces blocking by storing a version of data that one application can read while another is modifying the same data. Indicates that from one transaction you cannot see changes made in other transactions, even if IsolationLevel Enumeration Isolation Levels in Database Engine SET TRANSACTION ISOLATION LEVEL (Transact-SQL)

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