Oracle Processes - Expert Oracle Database Architecture - page 186

There are two classes of background processes: those that have a focused job to do (as just described) and those
that do a variety of other jobs (i.e., utility processes). For example, there is a utility background process for the internal
job queues accessible via the DBMS_JOB/DBMS_SCHEDULER packages. This process monitors the job queues and runs
whatever is inside them. In many respects, it resembles a dedicated server process, but without a client connection.
Let's examine each of these background processes, starting with the ones that have a focused job, and then look into
the utility processes.

Focused Background Processes
The number, names, and types of focused background processes varies by release. Figure 5-4 depicts a typical set of
Oracle background processes that have a focused purpose:

Clustered
Instances

Shared Memory
Network
Disk I/O

LMDO

LCKn

LMSn

LMON

PMON

Block Buffers Redo Log

SMON

SGA

RBCO

CKPT DBWn LGWR ARCn

Database
Files

Remote
Database

Archive
Logs

Online Redo

Figure 5-4. Focused background processes

■ For a complete diagram showing all Oracle 12 c background processes and memory structures, see the file at
www.oracle.com/technetwork/tutorials/posterfiles-1974103.pdf .

Tip

For example, in Oracle 12 c Release 1, here's a database started using a minimum number of init.ora
parameters.

SYS@ORA12CR1> create pfile='/tmp/pfile' from spfile;
File created.