tailieunhanh - Appendix B sample test 730

Welcome to the section that really makes this book unique. In my opinion, one of the best ways to prepare for the DB2 9 Fundamentals certification exam (Exam 730) is by answering sample questions that are presented in the same format that you will see when you take the certification exam. In this section you will find 150 sample questions, along with comprehensive answers for every question. (It s not enough to know which answer is correct; it s also important to know why the answer is correct and why the other choices are wrong!). | The correct answer is D. When the Uncommitted Read isolation level is used, rows retrieved by a transaction are only locked if the transaction modifies data associated with one or more rows retrieved or if another transaction attempts to drop or alter the table the rows were retrieved from.) As the name implies, transactions running under the uncommitted read isolation level can see changes made to rows by other transactions before those changes have been committed. On the other hand, transactions running under the Repeatable Read, Read Stability, or Cursor Stability isolation level are prohibited from seeing uncommitted data. Therefore, applications running under the Uncommitted Read isolation level can read the row Application A updated while applications running under a different isolation level cannot. Because no locks are needed in order for Application A to read data stored in other tables, it can do so – even if a restrictive lock is held on that table. However, there is nothing that prohibits Application A from performing an insert operation from within the open transaction.