ORACLE A RDBMS
INTRODUCTION
Oracle is relational database management system, which organizes data in the form of tables. Oracle makes efficient use of all system resources, on all hardware architecture, to deliver unmatched performance, price performance and scalability. Any DBMS to be called, as RDBMS has to be satisfied Dr.E.F.CODD rules that are called as father of RDBMS.
Dr.E.F.CODD’S RULES :
These rules are used for evaluation a product to be called as relational DBMS out of 12 rules a RDBMS product should satisfy at least 6 rules plus a rule called zero rule that must be satisfied.
The rules are as follows:
Rule 0 : Relational Database Management :
A relational database management system uses only its relational capabilities to manage the information stored in its database.
Rule 1 : Information Representation :
All information stored in a relational database is represented only by data item values, which are stored in the tables that make up the database. Associations between data items are not logically represented in any other way, such as, by the use of pointers from one table to another.
Rule 2 : Logical Accessibility :
Every data item value stored in a relational database is accessible by starting the name of the table it is stored in, the name of the column under which it is stored and the value of the primary key that defines the row in which it is stored.
Rule 3 : Representation of null values :
The database management system has a consistent method for representing null values. For example, null values for numeric data must be distinct from zero or any other numeric value and for character data it must be different from a string of blanks or any other character value.
Rule 4 : Catalog Features :
The logical description of a relational database is represented in the same manner as ordinary data. This is done so that the facilities of the relational database management system itself can be used to maintain database description.
Rule 5 : Data Language :
The relational database management system may support many types of for describing data and accessing the database. However, there must be at least one language that uses ordinary character strings to support the definition of data, the definition of views, the manipulation of data integrity, information concerning authorization and the boundaries for recovery of units.
Rule 6 : View Updatability :
Any view that can be defined using combination of base tables, that are theoretically updateable, is capable of being updated by the relational database management system.
Rule 7 : Insert, Update and Delete :
Any operand that describes the results of a single retrieval operation is capable of being applied to an insert, update or delete operation as well.
Rule 8 : Physical Data Independence :
Changes made to physical storage representation or access methods do not require changes to be made to application programs.
Rule 9 : Logical Data Independence :
Changes made to tables, that do not modify any data stored in that table, do not require changes to be made to application programs.
Rule 10 : Integrity Constraints :
Constants that apply to entity integrity and referential integrity are specifiable by the data language implemented by the database management system and not by the statements coded into the application program.
Rule 11 : Database Distribution :
The data language implemented by the relational management system supports the ability to distribute the database without requiring changes to be made to application programs. This facility must be provided in the data language. This facility must be provided in data language, whether or not the database management system itself supports distributed databases.
Rule 12 : Non Subversion :
If the relational database management system supports facility that allow application programs to operate on the tables a row at a time, an application program using this type of database access is prevented from bypassing entity integrity or referential integrity constraints that are defined for the database.
Distributed Systems: Oracle combines the data physically located on different computer into one logical database that can be accessed by all n/w users.
Probability: Oracle software is ported to work under different operating and is the same on all systems applications developed for oracle can be opted to any operating system with little or no modification.
Compatibility: Application developed for oracle can be used on virtually and system with little or no modification.
Connectability: Oracle software allows different types of computers and systems to share information access networks.