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The Locking Protocol: To manage concurrency related problems we use locking. A lock is mainly a variable that is associated with a data item in the database. A lock can be located by a transaction on a shared resource that it needs to use. When this is completed, the data item is available for the exclusive use for that transaction that is other transactions are locked out of that data item. When the transaction that has locked a data item does not need to use it any longer, it should unlock the data item so that other transactions can use it. If a transaction attempts to lock a data item already locked by some other transaction, it cannot do so and remains for the data item to be unlocked. The parts of DBMS that controls and stores lock information is known as the Lock Manager. The locking mechanism helps us to change a schedule into a serialisable schedule. We had definite what a schedule is, but what serialisable schedule is?
E-R model uses this symbol to represent weak entity set ? A Doubly outlined rectangle symbol is used to represent weak entity set.
management information system based on functional organisation
Find the names of all Albums that have more than 30 tracks. Result: (name: varchar(255))
What are the Constituents of File? Also elaborates all the possible file operations? A file is organised logically as sequence of record. These records are mapped onto disk blo
10A.53 Code an Oracle Database trigger to enforce the constraint that an employee can never change his or her department. 10A.54 Code an Oracle Database trigger to allow the
discuss the purpose of the concurrency control?
Explain the Difference between DROP and DELETE DELETE deletes one or more than one tuples of a particular relation from the database. DROP is employed to remove a table from th
read-set(T) : Each data items that are read by a transaction T Timestamps : for all transaction T, the start-time and the end time are reserved for all the three phases.
Attributes that are directly kept in the data base. For example, 'Birth date' attribute of a person. Derived Attributes that are not stored directly but can be derived
anyone have a textbook solutions case fair, 8 edition of vol 1 ?, please give me
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