Data Dictionary and Dynamic Performance Views

[Lachlann]

I am using oracle database and need to know the information about the tables which is being used in database.If I talk about the table which is created by myself,How much space it is taking in memory.How would I get the information .
You help will be great for me. Is there any tool or third party software should be installed with database through which I can access .If it's like so please introduce me about that.....Thanks.

[Praetor]

The data dictionary of database :

The data dictionary is the collective name of different tables which is used to access the administrative metadata for database.It provides the following information about :

1- The whole definition of schema object of database and with integrity constraint information.
2- The current space is being used by database objects in database.
3- Provides the information about the user and the granted privileges.

It is the central part of database.Oracle Database stores data dictionary data in tables as other.

[Katty]

Contents of oracle database :

The data dictionary contains the following two types of Objects :

1- Base table and
2- Views

• The Base table

is the collection of some underlying tables which stores information about database.The database is only have permission to read and write.User can't access these tables because the information on these tables is in encrypted format and user can't understand this format.

• The Views

are the decoded format of the base tables,it captures the information from the base table and respond to the user queries.Some views are accessible by every users whereas others are intended for administrators only.

[kelfro]

Dynamic Performance Views :

Due to this operation, Oracle Database generates a set of virtual tables which stores the current database activity.These views are called as dynamic performance views.They are also called as V$ views,contain information such as the following:

• System and session related parameters
• Current Memory usage and allocation
• File status with RMAN backup files
• Progress of jobs and tasks
• SQL execution
• Statistics and metrics

It has some usage below :
1. OEM uses this to get information about database
2. These views can be used by DBAs for performance and debugging of database.

[Zecho]

The contents of Dynamic performance views:

The dynamic performance views are treated as fixed views because the administrator or any user of database can't alter and remove the contents of these views.

The dynamic views are kept in the SYS schema. When you will go to create the database using DBCA (Database Configuration Assistance),oracle creates these views automatically.catalog.sql script is being used to create the dynamic views and contains the structure of views and public synonyms for the dynamic performance views.