Oracle Data Dictionary

The Oracle data dictionary is generally made up of a dictionary of tables and indexes along with various Oracle-provided packages, procedures and functions.

• Data Dictionary - the metadata or the data describing the format of the user data.
• Virtual Table - dynamic performance tables or views or the Dollar ($) tables. These tables can be used to assess database performance.
• View - a view is a logical overlay mapping over a single or a number of tables.
• Packages - packages are used to logically group stored procedures. In terms of the data dictionary there are various built-in packages containing sets of procedures provided by Oracle.
• Procedures - a stored procedure is stored and compiled into the database. These stored procedures are stored in the SYSTEM tablespace as part of the data dictionary.
• Functions - as with stored procedures a function is simply a procedure which returns a value.
• SQL - structured query language is the language used to access a relational database.

These Data Dictionary web pages will attempt to explain the following. Included will be the Oracle database data dictionary plus the Oracle provided packages, procedures and functions.

• Mining the data dictionary.
• Structuring the data dictionary.
• Using DBMS packages.
• Using SQL.

The data dictionary is the data about the data. Data about data is called Metadata. The Metadata is the data which describes the data. The data dictionary contains the definitions of tables. The tables are where actual data is added to. Metadata is the details containing data types, lengths,precisions and which data items are contained within which objects. All details of tables, indexes, synonyms, views, grants, roles, etc. are contained within the data dictionary.