Introduction

1. Introduction History 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

2. Advantages of RDBMS • Advantages : • Uses OOPs (Object-Oriented Programming ) concept. • Highly secured • Multiple users can access which is not possible in DBMS. • It is relational. • Avoids data redundancy problems using NORMAL FORMS • It performs all DML operations which is not possible with ordinary DBMS (it performs only INSERT & RETRIEVE) • Supports data Independence. • finally it supports DDBMS concepts too and so on. • Scalability • Reliability • Single development model • Common skill set • One management interface • One vendor

3. Advantages of rdbms 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

4. 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.

5. 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

6. DBMS V/s RDMBS

7. Basic Concept of Database: Database is collection of meaningful or designed data which is used for a specific purpose There are three type of database 1.Network database 2.Hierarchical database 3.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

8. ORACLE ARCHITECTURE Oracle Tools The Oracle product is divided into two parts as • Oracle server tools • 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 or Oracle workshop server The 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 as • Memory structures • Background processes • Disk resources management Oracle Database Various disk management Process Components Memory components

9. 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.

10. Oracle Database Architecture Via SQL *Net listener Multithreaded server Snnn Dnnn User Proce. Shared pool PMON SGA PGA Buffer cache To distributed database nodes Private Redo log buffer DBWR LGWR CKPT RECO LCKn Archive destination SMON Redo Logs Data1.dbf Data2.dbf Data3.dbf ARCH Init .ora Control files

11. 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 shared pool The redo log buffer The Buffer cache

12. 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 components The required components contain • Library cache and • Dictionary cash While in optional components session information is stored Library 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

13. 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

14. 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 are 1.DBWR:- The database writes process which the changed block from buffer cache to disk LGWR:- 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 files It 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 occurred SMON:- 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 process ARCHIVER:-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.

15. Overview of Primary Components Instance User SGA process Shared Pool Library Redo Log Database Cache Buffer Buffer Cache Server Data Dictionary process Cache Large Pool Java Pool PGA PMON SMON DBWR LGWR CKPT Others Control Data Redo Log files Parameter files Archived files file Log files Password file Database 1 - 2