Oracle 19c Architectural components Part 3

Oracle Background Processes

Background processes are part of the database instance and perform maintenance tasks required to operate the database and to maximize performance for multiple users. Each background process performs a unique task, but works with the other processes. Oracle Database creates background processes automatically when you start a database instance. The background processes that are present depend on the features that are being used in the database. When you start a database instance, mandatory background processes automatically start. You can start optional background processes later as required.

Mandatory background processes are present in all typical database configurations. These processes run by default in a read/write database instance started with a minimally configured initialization parameter file. A read-only database instance disables some of these processes. Mandatory background processes include the
Process Monitor Process (PMON), Process Manager Process (PMAN), Listener Registration Process (LREG), System Monitor Process (SMON), Database Writer Process (DBWn), Checkpoint Process (CKPT), Manageability Monitor Process (MMON), Manageability Monitor Lite Process (MMNL), Recoverer Process (RECO), and Log Writer Process (LGWR).

Oracle 19c Architectural components Part 2

System Global Area

Oracle 19c SGA

The System Global Area (SGA) is the memory area that contains data and control information for one Oracle Database instance. All server and background processes share the SGA. When you start a database instance, the amount of memory allocated for the SGA is displayed. The SGA includes the following data structures:

Oracle 19c Architectural components Part 1

An Oracle Database consists of at least one database instance and one database. The database instance handles memory and processes. The database consists of physical files called data files, and can be a non-container database or a multitenant container database. An Oracle Database also uses several database system files during its operation.

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