DBMS Database Management System - Technical Questions and Answers

DBMS - Database Management System
DBMS - Basics

41.	Explain the difference between an exclusive lock and a shared lock.
	Answer: An exclusive lock prohibits other users from reading the locked resource; a shared lock allows other users to read the locked resource, but they cannot update it. Workspace Report errors ... Name : Email: View Answer

42.	Explain the difference between optimistic locking and pessimistic locking.
	Answer: Optimistic locking assumes no transaction conflict will occur and deals with the consequences if it does. Pessimistic locking assumes that conflict will occur and so prevents it ahead of time with locks. In general, optimistic locking is preferred for the Internet and for many intranet applications. Workspace Report errors ... Name : Email: View Answer

43.	What is deadlock? How can it be avoided? How can it be resolved once it occurs?
	Answer: Deadlock occurs when two transactions are each waiting on a resource that the other transaction holds. Deadlock can be prevented by requiring transactions to acquire all locks at the same time; once it occurs, the only way to cure it is to abort one of the transactions and back out of partially completed work. Workspace Report errors ... Name : Email: View Answer

44.	What are the major functions of the database administrator?
	Answer: Managing database structure, controlling concurrent processing, managing processing rights and responsibilities, developing database security, providing for database recovery, managing the DBMS and maintaining the data repository. Workspace Report errors ... Name : Email: View Answer

45.

Explain what we mean by an ACID transaction.

46.	What are the ways in which an Oracle database can be created?
	Answer: There are three (3) ways to create an Oracle database. You can create a database using the Database Configuration Assistant, using the Oracle-supplied database creation procedures or using the SQL CREATE DATABASE command. Workspace Report errors ... Name : Email: View Answer

47.

What are sequences, and what are the possible problems when using them to create surrogate keys?

48.	Under what conditions should indexes be used?
	Answer: Indexes can be created to enforce uniqueness, to facilitate sorting, and to enable fast retrieval by column values. A good candidate for an index is a column that is frequently used with equal conditions in WHERE clauses. Workspace Report errors ... Name : Email: View Answer

49.

Explain the three levels of transaction isolation supported by Oracle.

50.	What are the types of files used in Oracle recovery?
	Answer: Datafiles, control files and two types of ReDo log files: OnLine Redo and Offline ReDo (which is also known as Archive ReDo). Workspace Report errors ... Name : Email: View Answer