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Explain Two phase locking protocol
A transaction is consider as to follow the two-phase locking protocol if all locking operations precede the first unlock operation in the transaction. Such type of transaction can be divided into two phases: and expanding or growing (first) phase, throughout which new locks on items can be acquired but none can be released; and a shrinking (second) phase, throughout which existing locks can be released but no new locks can be obtained. This two-phase protocol can make sure the serializability because all the data items needed by a transaction will be locked at the starting of the transaction and if other transaction needs to use those data items then it has to wait till they become unlocked.
What are audit trails? An audit trail is a log of all alters to the database along with information like which user performed the change and when the alter was performed.
It defines that the tuple in one relation that refers to another relation must refer to an existing tuple in that relation. This constraint is states on two relations (not essentia
Explain the two constraints, check and foreign key in SQL along with an example for each. Give the syntax. CHECK constraint - CHECK constraint specifies an expression which
What is data integrity? Ans: It is the data consisted of in database that is accurate and consistent. (Data integrity means that the data should be valid as per to the give
Complete replication: It implies maintaining of a whole copy of the database at every site. Thus, the reliability & availability and performance for query response are maximized.
Differance between Unordered and ordered file ? Unordered file do no has any sequence although ordered file has arranged in a few sequence and data are assigned in ordered form
Draw an ER diagram for company''s database schema
What are the two integrity rules? Ans: The two integrity rules are: Entity Integrity Rule & Referential Integrity Rule. Entity Integrity Rule - If the attribute A of rel
I am going to develop a web site to present decision tree structure. For this, I want a web application with AJAX technology to connect the database and prepare the decision tree's
Dependency Preservation It is obvious that the decomposition must be lossless so that we do not lose any information from the relation that is decomposed. Dependency preservati
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