Oracle Back Ground Process

Oracle instance refers to the combination of oracle background processes and memory structures. Here Oracle instance runs two types of processes. They are:
1. Server Processes
2. Background Processes

SERVER PROCESSES: Oracle creates server processes to handle requests from connected user processes. A server process is in charge of communicating with the process and interacting with oracle to carryout the requests of the associated user process.

For Example:
Let us say a user 'XXX' requests data from 'YYY' table. If the requested data is not available in the data base buffers of the System Global Area(SGA), then the associated server process is responsible for reads the data from the data files into the System Global Area.

BACKGROUND PROCESSES: Oracle Background processes as the name says these are the processes running behind the scene and are meant to perform certain maintenance tasks and or to deal with abnormal conditions arising in the  life time of the instance.


You can see the Oracle background processes with this query: 

SELECT * FROM V$SESSION WHERE TYPE='BACKGROUND';

Not all background processes are mandatory for an instance. Each background has its own specific purpose. Background processes are invoked automatically when the instance is started. Given below is a list of some of the background processes.

• Database Writer
• Log Writer
• Archiver
• System Monitor
• Process Monitor
• Checkpoint Process
• Lock Monitor
• Lock Manager Daemon
• Lock Processes
• Block Server processes
• Queue Monitor
• Event Monitor
• Recoverer
• Job Queue Processes
• Dispatcher
• Shared Server Processes
• Trace Writer