Wednesday 7 October 2015

Oracle DBA Interview Questions Part I

                                                                             

A database is an organized collection of information treated as a unit. The purpose of a database is to collect, store, and retrieve related information for use by database applications.

                                         
                            

1. What are the components of Physical database structure of Oracle Database?
ORACLE database is comprised of three types of files. One or more Data files, two are more Redo Log files, and one or more Control files.

2. What are the components of Logical database structure of ORACLE database?
Tablespaces and the Database's Schema Objects.

3. What is a Tablespace?
A database is divided into Logical Storage Unit called tablespaces. A tablespace is used to grouped related logical structures together.

4. What is SYSTEM tablespace and when is it Created?
Every ORACLE database contains a tablespace named SYSTEM, which is automatically created when the database is created. The SYSTEM tablespace always contains the data dictionary tables for the entire database.

5. Explain the relationship among Database, Tablespace and Data file.
Each databases logically divided into one or more tablespaces one or more data files are explicitly created for each tablespace.

6. What is schema?
A schema is collection of database objects of a User.

7. What are Schema Objects?
Schema objects are the logical structures that directly refer to the database's data. Schema objects include tables, views, sequences, synonyms, indexes, clusters, database triggers, procedures, functions packages and database links.

8. Can objects of the same Schema reside in different tablespaces?
Yes.

9. Can a Tablespace hold objects from different Schemes?
Yes.

10. What is Table?
A table is the basic unit of data storage in an ORACLE database. The tables of a database hold all of the user accessible data. Table data is stored in rows and columns.

11. What is a View?
A view is a virtual table. Every view has a Query attached to it. (The Query is a SELECT statement that identifies the columns and rows of the table(s) the view uses.)

12. Do View contain Data?
Views do not contain or store data.

13. Can a View based on another View?
Yes.

14. What are the advantages of Views?
Provide an additional level of table security, by restricting access to a predetermined set of rows and columns of a table.
Hide data complexity.
Simplify commands for the user.
Present the data in a different perspective from that of the base table.
Store complex queries.

15. What is a Sequence?
A sequence generates a serial list of unique numbers for numerical columns of a database's tables.

16. What is a Synonym?
A synonym is an alias for a table, view, sequence or program unit.

17. What are the type of Synonyms?
There are two types of Synonyms Private and Public.

18. What is a Private Synonyms?
A Private Synonyms can be accessed only by the owner.

19. What is a Public Synonyms?
A Public synonym can be accessed by any user on the database.

20. What are synonyms used for?
Synonyms are used to: Mask the real name and owner of an object.
Provide public access to an object
Provide location transparency for tables, views or program units of a remote database.
Simplify the SQL statements for database users.



Oracle DBA Interview Question -2

Oracle DBA Interview Question - 3

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