IntroductionHistory The principles of the relational model were first outlined by Dr. E.F Codd in a June 1970

paper is called “A Relational Model of Data fore large shared Data Banks” In this paper, Dr, Codd proposed the relational model for database system .

The more popular models used at that time were hierarchical and network, or even simple flat file data structures.

Relational database management systems (RDBMS) soon become very popular, especially for their ease of use and flexibility in structure.

In addition, a number of innovative vendors, such as oracle, supplemented the RDBMS with a suite of powerful application development and user product, providing a total solution.

Components of the Relational model- Collection of objects or relations that store the data- Set of operator to act on the relations to produce other relations- Data integrity for accuracy and consistency

Advantages of RDBMS Advantages :

1. Uses OOPs (Object-Oriented Programming ) concept. 2. Highly secured 3. Multiple users can access which is not possible in DBMS. 4. It is relational. 5. Avoids data redundancy problems using NORMAL FORMS 6. It performs all DML operations which is not possible with

ordinary DBMS (it performs only INSERT & RETRIEVE) 7. Supports data Independence.8. finally it supports DDBMS concepts too and so on.9. Scalability10. Reliability11. Single development model12. Common skill set 13. One management interface14. One vendor

15. Allow us to collect data in relatively 16. Simple table, 17. Keeping organization tasks simple.

18 We can much data from one table to corresponding( same row) data in another table by using a linking mechanism called a relational join.

19. Match primary key in one table to a foreign Key in a second table

Advantages of rdbms

Disadvantages of RDBMS:-Or Limitation of RDBMS

Advantage is More secure and Normalization (reducing Redundancy, repetition, concurrency), avoiding problems while processing 2 things at a time. (while these are not possible in file processing systems)

Disadvantage is it requires more knowledge to implement.

RDBMS:-A relational database is a collection of relations or two-dimension table is called RDBMS

A relational database user relational or two-dimensional table to store information.

Example:-You might want to store information about all the employee in your company. In relational database, you create several table to store different pieces of information about your employees such a as an employee table and a salary table

DBMS RDBMS

In DBMS relationship between two table or file are maintained programmatically

In RDBMS relationship between two tables or files can be specified at the time of table creation

DBMS dose not support client/server Architecture Most of the RDBMS support client/server Architecture

DBMS does not support distributed database Most of the RDBMS support distributed database

In DBMS there is no security of data In RDBMS there are multiple levels of security

1) logging in at O/s level

2)Command level

3)Object level

Each table is given an extension in DBMS Many table are grouped in one database in RDBMS

DBMS may satisfy less than 7 to 8 rules of Dr .E.F codd

RDBMS usually satisfy less than 7 to 8 rules of

Dr .E.F codd

Field Column, Attributes

Record Row, Tuple, Entity

File Table, Relation, Entity class

DBMS V/s RDMBS

Basic Concept of Database:Database is collection of meaningful or designed data which is used for a

specific purpose

There are three type of database1.Network database2.Hierarchical database3.Relational database

Network and Hierarchical database uses a pointer to access the record but in case of relational database records are accessed by the value stored in the table

A system which help user in managing data in a database is called database management system. (DBMS)

Oracle 8i is not 100% RDBMS since it does not obey all codd’s Rule

ORACLE ARCHITECTUREOracle ToolsThe Oracle product is divided into two parts as1. Oracle server tools2. Oracle Client tools

Oracle server tools:-The oracle server is a program installed on the server’s hard disk. This program first get

loaded in Ram and then user request will get processed.The oracle server product having two types-Oracle Enterprise server orOracle workshop serverThe functionality of both is identical but the main difference between these product is

oracle workshop server restricts the number of users who can query the server whereas the oracle enterprise server has no such restriction

The oracle server consists of many different components as1. Memory structures2. Background processes3. Disk resources management Oracle Database

Various disk management Memory components Process Components

Oracle Instance:-The combination of memory buffer and background processes is called as an

oracle instance, An instance has two types of processes

1)Oracle Processes: include two process a) Server processes: Which do the work for the user b) Background Processes: Which do the maintenance work of the oracle server

2) User Processes:- Executes the code of the an application program which includes oracle client tool such as oracle is Forms, oracle repots etc.

Dnnn

Via SQL *Net listener

UserProce.

Snnn

Multithreaded server

PGA SGA

Archivedestination

DBWR

SMON

CKPTLGWR

LCKnRECO

ARCHRedoLogs

Control filesInit .ora

To distributed database nodes

PMON

Buffer cache

Data1.dbfData2.dbfData3.dbf

Private

Shared pool

Redo log buffer

Oracle Database Architecture

Memory Structure:- This set of memory components represents a ‘living version of oracle

that is available only when an instance is running. two basic memory structure are

1.System Global area (SGA)2.Program Global Area (PGA)

System global area (SGA):-This is the most important memory structure in oracle .SGA and background

processes from an oracle instance. each instance has its own SGA

System Global Area

The Buffer cache The shared pool The redo log buffer

These are the fixed sizes and are created during the instance initialization.1.The Buffer cache:- The database buffer cache consists it set of database buffers of an instance. The

database buffer stores the data block which is used most recently by the user. It contains modified and non _modified blocks. It improves the performance since the data store in buffer cache is the most recently used data block, so less I/O to and from disk transaction are done

2.Shared pool:- The shared pool contains shared structures such as the SQL shared area. It

consists of required components and optional componentsThe required components contain• Library cache and• Dictionary cash

While in optional components session information is storedLibrary cache:- Library cache use to store the parse information for SQL statements executing

against the database. The parse information includes the set of database operation that the SQL execution mechanism will perform in order to obtain data requests by the user processed the parse information is a shared resources in library cash but the data returned by the query for each user will not reside in the share pool and thus it is not shared as it is a question of integrity or security issue

Dictionary cache:-Dictionary cache stores data from the oracle data dictionary. Oracle data dictionary is used by oracle database for internal process as well as processed so it is beneficial to use the data dictionary cache to improve the performance.

Redo log buffer:-The redo log buffer stores redo entries to a memory area in order to keep tracing of database changes. Every process that makes a changes to the database must write an entry to the redo log in order to allow oracle to recovers the changes

When database is setup to archive redo logs, these database changes are kept in order to rebuild database objects in events of disk failure.

Program global area (PGA):-A PGA is created by oracle when a server process is initiated. The program global area is a memory buffer containing data and control information for a server process

Oracle background processes:-Oracle creates a set of background processes for each instance. The background process asynchronously execute the I/O and monitor other oracle process, gives better performance and reliability.The some of background processes are1.DBWR:- The database writes process which the changed block from buffer cache to diskLGWR:- log Writer- It writes redo log entries from redo log butter to online redo log files on disk. It also writes log sequence number of current redo log to data files headers and control filesIt handles initialing the process of clearing the dirty buffer write queue.CKPT:- check point- Update block are written to disk by DBWR when the event called checkpoint is occurredSMON:- system monitor process: when oracle instances failed, SMON handles this recovery i.e. instances failure is hands by SMON.PMON:- Process Monitor- PMON executes the recovery when a user process on database fails. It cleans up the buffer cash and free the resources use by the processARCHIVER:-ARCH –it copies the online Redo files and stores the files on disk when they are full or when the log is switched. This is useful for database recovery in case of disk failure.

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Passwordfile

Overview of Primary Components

InstanceSGA

Redo LogBuffer

Shared Pool

Data DictionaryCache

LibraryCache

DBWRSMONPMON CKPTLGWR Others

Userprocess

Serverprocess

PGA

Control files

Data

files

Database

DatabaseBuffer Cache

Redo Log files

Java Pool Large Pool

Parameterfile

Archived Log files