Oracle Database Architecture
Without knowing the Oracle database architecture is hard to be an Oracle
DBA. Knowing the Oracle database architecture helps you to manage and to
troubleshoot the Oracle database.
The first things you have to know about the Oracle database architecture
a) the main Oracle processes:
| Oracle Process
|| Tasks performed
when a session is
restart the Dispatcher and server processes if they are stopped
registers information about the instance and dispatcher
processes with the network listener
||- when an instance is broken or
- a rollback is performed (INSTANCE RECOVERY).
In an Oracle Real Application Clusters database, the SMON
process of one instance can perform instance recovery for
other instances that have failed.
- cleans up temporary segments that are no longer in use
- coalesces contiguous free extents in dictionary managed
tablespaces that have PCTINCREASE set to a non-zero value.
|- writes modified blocks from the
database buffer cache to the data files.
The database selects an appropriate default setting
for this initialization parameter or adjusts a user-specified
setting based on the number of CPUs and the number of processor
groups. However, the
initialization parameter could be used to specifies the number
of DBWn processes. Oracle Database
allows a maximum of 20 database writer processes (DBW0-DBW9 and
||- write to disk the content of redo
||- tell to the DBWn to write the buffer
cache information to the disk files
(Coordinator Job Queue)
||- check for scheduled jobs create
processes Jnnn processes which will run the particular
(Job slave process)
||- run different scheduled jobs. For
more information about the
follow the link.
||- receive requests from the listener
and acts like a requests coordinator for the Oracle Shared (MTS)
Server processes. For more information about the
Server architecture follow the link.
||- archive the log files (if database
is in ARCHIVELOG mode).
Which is the difference between an Oracle database
and an Oracle instance
Also, I want to note that an instance has two major memory
structures: System Global Area (SGA): stores information in
memory shared by processes in Oracle and Program Global Area (PGA):
contains information private to a particular process.
What is an Oracle Listener
Oracle Shared vs. Dedicated Server Architecture
Oracle Service Name