Hour 14

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Quiz Answers

1:	What must be maintained when using the pessimistic concurrency approach? Locks on data resources Database connections Events
A1:	a and b. Both locks on data resources and database connections must be maintained in pessimistic concurrency.
2:	In general, how is optimistic concurrency implemented? Compare original values to current values in the data source Identify key changes, then commit updates Delete old values, then insert new values
A2:	a. In general, you will need to compare original values (that you read from the data source) to current values in the data source before the data can be updated. If any of the comparison fails (indicating that the row was updated by someone else), you have encountered an optimistic concurrency violation.
3:	True or false: Pessimistic concurrency is designed for fast, scalable applications in .NET.
A3:	False: Pessimistic concurrency is not designed for fast scalable applications in .NET because of the expensive need to hold connections and locks.
4:	What should be used when using the optimistic concurrency approach and XML? Blocks Tags DiffGrams
A4:	c. DiffGram s are an excellent XML structure to use when having to implement optimistic concurrency between varying systems. All that you need to test for optimistic concurrency violations is embedded in these block structures.

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