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The Processes
Background processes
- Part of the instance
- Started with the instance
- Provide database operations
- e.g. DBWR writes dirty block to database file
- Some are optional (ARC)
Server Processes
- Act on behalf of clients
- Two types
Notes:
There are two main categories of processes: background and server.
Oracle uses background processes to perform database operations such as writing dirty (updated) blocks in the buffer cache to database files. (You’ll learn more about these services as you progress through this lesson.) The background processes are part of the instance and are started at instance startup. Some, like DBWn, PMON, SMON, CKPT and LGWR are required. Others, such as ARCn, are optional.
Server processes act directly on behalf of the clients. For example, they accept, parse and execute the queries executed by users. During execution, they read blocks from the data files. Two types of server processes are available:
Dedicated server processes – These are called dedicated because they are dedicated to a single user for the life of the user’s session.
Shared Server Processes – These processes are shared among many clients. A dispatcher process is started to control access to the shared servers. The DBA must take steps to configure the “Shared Server” environment.
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