Oracle Interview Question

Oracle Interview Question

Q1: What is Oracle?

A1: Oracle is a database server that is used to handle data in a structured manner. It lets its users to retrieve and to store data in a way that multiple users can access similar data at the same time. Oracle achieves this with high efficiency. Many security checks are followed to limit access to authorized users only and to retrieve data in case of accidental data loss.


Q2: Define Oracle database.

A2: An Oracle database can be termed as a compilation of data housed in a database server and treated like a large unit.


Q3: Explain Oracle instance.

A3: Each operating Oracle database is associated with an Oracle instance. As soon as a database server starts the database, it is assigned a memory area by Oracle called System Global Area (SGA) and starts one or more than one processes. The SGA and Oracle processes together are referred to as an Oracle instance. The process and memory of an instance are used to efficiently handle data used by multiple users.


Q4:  Explain Parameter file in Oracle.

A4: It is a file having a track of initialization parameters and the matching values. The two types of Oracle supported parameter files are:


a)      Initialization parameter file – Text version and

b)       Server parameter file – Binary version


Based on individual installations users can specify their individual initialization parameters.


Q5: Explain Oracle’s Server parameter file.

A5: It is a file which has a binary nature and contains initialization parameter’s list. It is located machines where database server executes. Initialization parameters of server parameter file are persistent.


Q6: Explain Oracle’s initialization parameter file.

A6: It is a file which contains initialization parameter’s list. Basically it is a simple text file and is written in the default character set of the client. The changes are enforced when the machine is fully shut down and then restarted.


Q7: Explain Oracle’s System Global Area (SGA).

A7: It is the memory area which contains shared data like SQL statements shared pool and buffer cache, between all users. As soon as an Oracle database instance starts the SGA is allocated. Value changes become effective during subsequent startup.


Q8: Explain user account with reference to Oracle.

A8: Every user is given particular attributes identified by a user name termed as user account. The below can be incorporated in the user attributes:

a)      Passwords to access database,

b)      Roles and privileges,

c)      Default table space containing database objects and

d)     Default temporary table space facilitating query handling work space.


Q9: Which are the five query types?

A9: The five query types are as follows:

a)      Compound queries,

b)      Nested queries,

c)      Corelated queries,

d)     Sub queries and

e)      Normal queries.


Q10: What do you mean by a transaction?

A10: A group of SQL statements flanked by any 2 ROLLBACK and COMMIT statements is a transaction.