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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.
Define NULL value NULL value NULL means something is unknown. It does NOT mean null (the digit 0). Null is as well employed as attribute value for a particular entity in which
What are the various forms of data transparency? a) fragmentation transparency b) replication transparency c) location transparency
Explain Data Sublangauges ? Data sublanguage: In relational database theory, the term sublanguage, first used for this purpose through E. F. Codd in the year of 1970, refers t
Given the following set of functional dependencies {cf→ bg, g → d, cdg → f, b → de, d → c} defined on R(b,c,d,e,f,g) a. Is cf→ e implied by the FDs? b. Is dg a superkey?
Write the motivations led to development of OO-DBMS? 1. Programmer frustration with RDBMSs. 2. Requirement for special features.
Domain Constraints Domain constraints are primarily formed for defining the logically correct values for an attribute of a relation. The relation allows attributes of a relatio
Define tuple variable? Tuple variables are used for comparing two tuples in the same relation. The tuple variables are explained in the from clause by way of the as clause.
What are the situations while DBMS should not be used? DBMS should not be used in situations like: (i) No need of security. (ii) Not difficulty to access the data (iii) N
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