ORACLE ARCHITECTURE -1
What is DATABASE ?
A 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
- 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
- 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 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
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