Oracle Architecture basic questions & ans part-1

1)What is the command to find the database that already present before connecting ?

In Unix: ps -ef | grep pmon
In Windows: You can check the database service is runnig or not.


2)What are the components of Physical database structure of Oracle Database?


the phycial structures of the database are
1.datafile
2.redologfile
3.control file
datafile:- datafile contains actial data of the database.
redologfile:- it contains all changes done to the data base.it works in the circular fashion.
controlfile:- it contains status and structure of the database.

3)What are the components of Logical database structure of ORACLE database?

Tablespaces--->Segments---->Extents----->Data Blocks.


4)What is a Tablespace?

It is a Logical area of storage in a Database that directly corresponds to one or more physical files.


5)What is SYSTEM tablespace and when is it Created?

Every Oracle Database contains a tablespace called system tablespace.This tablespace gets created at the time of database creation and it holds data dictionary information for the entire database.

6)Explain the relationship among Database, Tablespace and Data file?


i)A DATA IN A DATABSE IS STORED PHYSICALLY IN A DATAFILE AND LOGICALLY IN A TABLESPACE.
ii)A TABLESPACE CAN BELONG TO ONLY ONE DATABASE AT A TIME.
iii)A DATABASE CAN CONTAIN MORE THAN ON TABLESPACE.
iv)A TABLESPACE CAN CONTAIN ONE OR MORE DATAFLES.
v)A DATAFILE CAN BELONG TO ONLY ONE TABLESPACE AND ONE DATABASE .

7)Can a Tablespace hold objects from different Schemes ?

Yes



8)What is schema?

Schema is a Collection of Database objects of a user.
Example: Tables Views Synonyms Sequences Clusters Triggers Procedures Packages.

9)Can objects of the same Schema reside in different tablespaces.?

Yes

10)What is a Data Dictionary ?
The data dictionary of an ORACLE database is a set of tables and views that are used as a read-only reference about the database.
It stores information about both the logical and physical structure of the database, the valid users of an ORACLE database, integrity constraints defined for tables in the database and space allocated for a schema object and how much of it is being used.