Oracle and its process
https://www.computersprofessor.com/2016/04/oracle-and-its-process.html
INTRODUCTION:
Oracle is an RDBMS software provided by oracle
development software cor poration .The RDBMS software supports the user
declarative statements which describe the rules that the data must satisfy. Thus,
an RDBMS provides all the users a facility to store & retrieve data in a consistent
manner with a defined model called, RELATIONAL MODEL
ORACLE is
also known as ORDBMS (OBJECT RELATIONAL DATABASE MANAGEMENT SYSTEM) which
offers both relational & object oriented data base systems. Hence, Objects
can be defined as REUSABLE SOFTWARE CODE, which are location independent and perform
a specific task on any application environment with a little changes or no
change at all, to the code.
Oracle products are based on client / server
architecture technology. It involves segregating the process of an application
between the systems. The server performs all the activities related to the
database. The activities that help the user to interact with the application
called CLIENT. The clients request the information to the Server (Backend
Process) and Server responds to the Clients (Front end) after process.
S.G.A (SYSTEM GLOBAL AREA)
When
oracle is loaded from a oracle server, certain background process & memory
area is required for the oracle to run is allocated. The main memory area (or) virtual
memory that will be allocated by the system is called S.G.A The combination of
SGA and background processes together is an oracle database administrator. When
the database is running, the SGA is the centre of oracle activity. It provides
a communication between the user & back ground processes.
The SGA is having three CACHES , i.e.,
means of a storage area.
1.
STORED POOL
2.
REDO BUFFER
3.
DATABASE BUFFER
Thus, oracle
processes are divided into 3 types, as,
1. SERVER PROCESS
2. USER PROCESS
3. BACKGROUND PROCESS
SERVER PROCESS:
The server
process communicates with users to perform tasks on behalf of the user such as
executing SQL commands/statements and returning the data to the user.
USER PROCESS:
The user process runs on a special machine called the client
& server process runs on a server. Every client or user has a corresponding
dedicated server process running on its behalf.
The user process is created whenever an application, or oracle
tools connects to the database.
BACKGROUND PROCESS:
The back ground process perform the tasks related to the
database.
The four important process are,
a) DATABASE
WRITER
b) LOG
WRITER
c) PROCESS MONITOR
d) SYSTEM MONITOR
DATABASE WRITER (DBWR):
The database writer is responsible for writing
data in the database buffer to the secondary storage. Database buffers are the storage
locations in SGA.
LOG WRITER (LGWR):
The log writer writes the data in the
redo buffer to the redo mode files in the disk. They are used to recover the
database, in case of a database crash.
Process monitor (PMON) :
The process monitor is responsible for
managing the user processes connected to the database.
System monitor (SMON):
The system monitor is responsible for
managing the user for various processes associated with the database.
Further,
the relational database model has classified into three components
1. Structural component is to
build the data model
a.
Relational Objects (Tables)
b.
Attributes (also known as,
columns)
c.
Rows (tuples).
2.Integrity components which
is the component to manipulate the
structure.
3. Integrity
components which define the operational rules on the data.
Thus, the general function provided by the DBMS is shielding of the database users from hardware level details. In other words, the DBMS provides users with a perception of the database i.e., elevated some what about the hardware level and it supports user option.
Thus, the general function provided by the DBMS is shielding of the database users from hardware level details. In other words, the DBMS provides users with a perception of the database i.e., elevated some what about the hardware level and it supports user option.