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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
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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
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
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 V/s RDMBS
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
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
ORACLE ARCHITECTURE
Oracle Tools
The Oracle product is divided into two parts as
1.
Oracle server tools
2.
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 typesOracle 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
1.
Memory structures
2.
Background processes
3.
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.
Oracle Database Architecture
Via SQL *Net listener
Multithreaded server
User
Proce.
Snnn
Dnnn
Shared pool
PMON
SGA
PGA
To distributed
database nodes
Buffer cache
Private
Redo log buffer
LGWR
RECO
CKPT
DBWR
LCKn
SMON
Archive
destination
ARCH
Init .ora
Data1.dbf
Data2.dbf
Data3.dbf
Redo
Logs
Control files
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 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
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 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.
Overview of Primary Components
User
process
Shared Pool
Library
Cache
Server
process
Data Dictionary
Cache
Instance
SGA
Database
Buffer Cache
Redo Log
Buffer
Java Pool
Large Pool
PGA
PMON SMON DBWR LGWR CKPT Others
Parameter
file
Data
files
Control
files
Redo Log
files
Password
file
Database
1-
2
Archived
Log files