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Explain Strict Two-Phase locking
A transaction T does not release any type of its exclusive (X) locks until that transaction commits or aborts. In this method no other transaction can access the item which is written by T unless the transaction T commits. This is a better method than the two discussed.
In 2PL, a transaction may not be capable to release its locks even after make use of it. The data item will stay locked until the transaction ends all the actions on all the data items. If each transaction in a schedule follows 2PL after that conflict serializability can be made sure. This is since if the schedule is not serializable, the precedence graph for schedule S contains transactions T1, T2 ..... Tn will have a cycle ... assume that a cycle consists of T1, T2 ..... Tn ,T1. The meaning of this is that a lock operation by T2 is followed by an unlock operation by T1; A Lockoperation T3 is followed by an unlock operation by T2 ... and etc. Though this is a contradiction of the assertion that T1 is by using two phase locking protocol. So the assumption that graph is having a cycle is wrong and therefore S is serializable.
Consistency: This property makes sure that a complete transaction implementation takes a database from one consistent state to another consistent state. If the transaction fails e
Question: (a) What is ODBC and what is its function? (b) What is Web application server, and how does it work from a database perspective? (c) What does e-commerce mean
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Load sample data into the database tables design and test queries to return the following information • All rows and columns for employees • All rows and columns for customers •
Why Like predicate used for? LIKE predicate: The LIKE predicate searches for strings in which have a certain pattern.
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Using Literal Character String Example: To print IS A as one string with column name employee SELECT ENAME || ' IS A ' || JOB AS "EMPLOYEE" FROM EMP;
Define a table in SQL known as Client that is used to store information about the clients. Define CLIENT_NO as the primary key whose first letter must begin with ‘C'. Also ensure t
Entity types that do not have any key attribute, and therefore cannot be identified independently, are known as weak entity types. A weak entity can be recognized uniquely only by
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