As Oracle DBA, we all
know Oracle database server is combination of physical files, processes and
memory, in this article we are going to discuss about different files involved
in oracle database architecture
There are 3 most
important files
·
Data files
·
Control files
·
Redo logs file
There are other
supplementary files as well - parameter files, password files, archive log
files
Let’s discuss some more
details
Datafiles
Data files contains
actual data of the database, data files are formatted as per block size
designed during database setup.
There are few types of
datafiles
1.
SYSTEM - this includes system datafile and is critical to
database, it includes dictionary of the database
2.
User
datafile - this includes
application specific datafiles and contains application data and can be
customized as per requirement
3.
UNDO datafile - It holds old data while performing
activity in database like select, insert, update, delete, this old data can be
used to revert the changes in case of recovery
4.
TEMP datafile - In case user orders data based on select
query, it needs space to sort the data before returning back to user, first
sorting operation is performed in memory and if memory is not sufficient then
it moves to temp tablespace.
Control
Files
Control file contains
structure of the database like location of all datafiles, redo logfiles.
This is Critical file to
operation of database, and it is one of first file read by instance at startup.
Redo
logfile
This file contains
changes made to the database and can be used for recovery of processes.
copies of redo logfile
are called as archived log files.
Other files in oracle
database
Password file - this file authenticates the use who is capable to
startup the database.
parameter files-
This file
contains list of parameters used by instance. typically, there are two
types of parameter files
PFILE - text based parameter file, change to parameter
needs to be modified/added manually in file and restart is required to get it into
effect.
SPFILE - binary parameter file, change to the parameter
can be carried out on the go.