Hands-On 02 (Oracle Background Processes)

As a DBA, you are responsible to monitor and understand the functions of the Oracle background processes. Your job’s responsibilities dictate that you should at least be informed on the following basic fundamental subjects:

Oracle Background Processes

V$BGPROCESS

PMON

DBWn

ARC0

CKPT

SMON

RECO

Archive log configurations

ARCHIVE LOG LIST

DATABASE LOG MODE

The NOARCHIVELOG mode

The ARCHIVELOG mode

Commands:

ARCHIVE LOG LIST

-- Hands-On 02 (Oracle Background Processes)
-- Preparation
set echo on
connect system/manager as sysdba
SET linesize 1000 pagesize 55
COL name FORMAT a30
col description format a30
pause

--Start

CLEAR SCR
-- In this exercise you will learn how to check the 
-- Oracle background processes and see what the Archive, 
-- Log Writer, DB Writer, Checkpoint, and the SMON process,
-- etc...

-- Connect to SQLPlus as the SYSTEM/MANAGER user.

pause

CONNECT system/manager AS SYSDBA

pause

CLEAR SCR
-- Only view all the active Oracle background processes.

pause

SELECT * FROM v$bgprocess
WHERE PADDR <> '00'
/

-- This is the list of all the active background processes running
-- in this database.

pause

CLEAR SCR
-- Please note the following:
-- PMON - The Process Monitor (PMON) is responsible for performing
-- recovery if a user process fails and rolls back the uncommitted
-- transactions.

-- DBWn - The Database Writer (DBWn) is responsible for writing the 
-- changed blocks or dirty blocks in the database.

-- ARC0 - The Archiver (ARC0) is responsible for writing the Online
-- redo log files into the archive log destination.

-- LGWR - The Log Writer (LGWR) is responsible for writing data 
-- from redo log buffers to the online redo log files.

-- CKPT - The checkpoint process (CKPT) is responsible for synchronizing 
-- the buffer cache with the data file. It updates all datafile 
-- headers and the control files.

-- SMON - The System Monitor process (SMON) is responsible for instance
-- recovery.

-- RECO - The Recoverer Process (RECO) is responsible for performing
-- recovery of in-doubt transactions that often occur in distributed
-- transactions.
pause
pause

CLEAR SCR
-- As we mentioned, the Archiver (ARC0) is responsible for writing
-- the Online redo log files into the archive log destination.

-- The database archives the Online Redo Log files so that DBAs can
-- recover, to a point of failure, and to a point of time in case
-- of a disaster and/or a media failure.

-- In order to recover to the point of failure the database must 
-- be in the archivelog mode.

-- Check to see if the database is in the archivelog mode.

pause

ARCHIVE LOG LIST
/

pause

CLEAR SCR
-- Notice that the DATABASE LOG MODE should be in archivelog mode.
-- The automatic archival option must be enabled so that the Archive 
-- process will be able to archive the Online Redo log file into the
-- Archive destination. 

-- Make sure that you have enough disk space in the Archive destination.

-- On the one of our Hands-On exercises, we well discuss how to change
-- the database mode from the NOARCHIVELOG mode to the ARCHIVELOG mode.

pause
pause

CLEAR SCR
-- Now, you should practice this Hands-On exercise.

-- For more information about the subject, you are encouraged
-- to read from a wide selection of available books.

-- Good luck.
--
pause
pause