Introduction to Oracle's system processes and primary roles

Overview of Oracle's main processes

Data write Process (DBWR): Responsible for writing changed data from the database buffer cache to the data file

Log write Process (LGWR): Writes changes in the redo log buffer to the online redo log file

System Monitoring (Smon): Check database consistency If necessary also initiates recovery of the database when the database is opened

Process monitoring (Pmon): Responsible for cleaning up resources when an Oracle process fails

Checkpoint process (CKPT): Updates the database state information in the control files and data files whenever changes in the buffer cache are permanently recorded in the database.

Archive process (ARCN): Backs up or archives a full log group at each log switch

Job Scheduler (CJQ): Responsible for scheduling and executing a defined job in the system to complete some predefined tasks.

Recovery process (RECO): To ensure the consistency of distributed transactions, in the distributed transaction, either commit at the same time, or simultaneously rollback;

The legend illustrates the main process of Oracle

In the middle of this diagram is the SGA. The upper is Reco,pmon, and the Smon process, in which the two-way arrows indicate the communication between each process and the instance. The lower left side is the DBW0 and LGWR processes, each of which communicates with the redo log buffers, respectively, and the data buffers, while also accessing the data files and redo log files.
Other processes, such as ARC0, require access to offline storage devices and control files, and CKPT, which require access to data files and control files, are also shown in this diagram.

Introduction to Oracle's system processes and primary roles