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What is DATABASE ?

database is an organized collection of data, generally stored and accessed electronically from a computer system.

As a database administrator  we can say one more definition

A Database is a collection of  Logical level  and Physical level

In Logical level we have Database objects like

  • Tables
  • Views
  • Synonyms
  • Procedures
  • Packages
  • Tablespaces
  • Roles  Etc..,
  • These db objects we can access when database is up and running.


In Physical level we have file like CRD file

C stands for control file.

R stands for Redo log files

D stands for Data files

Control file :

  • Control file contains all the crucial information of database like


–>db creation time

–>Name  & locations of datafiles

–>Name  & locations of redolog files

–>Rman backup information

–>Archive information

  • Control file is used to start the database.
  • The size of control file is in lower MB’s
  • We can multiplex the control files to 8 different location(Min-1   Max-8)
  • We will give .ctl extension for the controlfile ,but the extension is not mandatory.It is understanding and only for our purpose.

Redolog file

  • Redolog file contains the latest transaction information
  • Redolog files are used for recovery purpose.
  • The size of redologfiles are lower in MB’s.
  • The extension of redolog file is.log(Not mandatory).
  • A group is a collection of members.
  • A member belongs to one group.
  • In a single database we can have of min-2 and max -16  groups.
  • In each group we can have min-1 and max-5 members.


  • These are largest in your database.
  • Datafiles  contains data
  • We have two types of Data


2.Business data


A data about data is known as Metadata.

Using metadata we can find out how many users and objects are existing and everything

Business data(Actual data) :

The actual data is known as Business data.

If we select anything .It will shows the data that is actual data.

Form version 6 to 12c we have CRD  files


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Note: Please test scripts in Non Prod before trying in Production.
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