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“Human beings, by
changing the inner attitudes of their minds, can change the
outer aspects of their lives.” William James (1842 - 1910) |
Read
first then play the video:
DBA-VIDEO -Oracle
Background Processes
Oracle Fundamentals II Case
Study
The Oracle Fundamentals II
Case Study consists of the numbers of the most common DBA tasks to do
its backup, recovery and network jobs. In your organization, you as a
DBA, are expected to know at least how to:: allocate and re-size the
memory space on the fly; understand the Oracle background processes;
multiplex the Control Files; configure the Database Archive mode;
Maintain Redo Log files; Duplex Archived Online Redo Log files;
User-Managed COLD or OFFLINE Backups; User-Managed HOT or ONLINE
backups; User-Managed Tablespaces and Datafiles backups; User-Managed
Tablespace Restoration; Backup and Recovery using the EXPORT and
IMPORT utilities; Create the RMAN repository; Use of the RMAN
commands; Configure of the RMAN tool; Use the RMAN backup utility;
Perform the recovery of a tablespace using the RMAN tool; Performing a
Complete Backup using the RMAN tool; Performing incomplete database
recoveries; Using the LIST and REPORT commands; Configuring a Listener
using the “Net Manager” tool; and Configuring a Service Name using
the “Net Manager” tool.
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"First they
ignore you, then they laugh at you, then they fight you, then
you win." - Mahatma Gandhi (1869-1948) |
Oracle Background Processes
Introduction
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$BGPROCESS
PMON
DBWn
ARC0
CKPT
SMON
RECO
Archive log configurations
ARCHIVE LOG LIST
DATABASE LOG MODE
The NOARCHIVELOG mode
The ARCHIVELOG mode
Commands:
ARCHIVE LOG LIST
Hands-on
Connect to a database
Connect to SQLPlus as the
SYSTEM/MANAGER user.
SQL> CONNECT
system/manager AS SYSDBA
View background processes
The Oracle Background
Processes are programs or tasks that run on the Oracle background such
as log writers, db writers, archives, checkpoint, etc.
Only view all the active
Oracle background processes.
SQL> SELECT * FROM
v$bgprocess
WHERE PADDR <> '00'
/
This is the list of all the
active background processes running in this database. 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.
Database Writer
DBWn - The Database Writer
(DBWn) is responsible for writing the changed blocks or dirty blocks
in the database.
Archiver
ARC0 - The Archiver (ARC0)
is responsible for writing the Online redo log files into the archive
log destination.
Log writer
LGWR - The Log Writer (LGWR)
is responsible for writing data from redo log buffers to the online
redo log files.
Checkpoint process
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.
System Monitor
SMON - The System Monitor
process (SMON) is responsible for instance recovery.
Recoverer
RECO - The Re-coverer
Process (RECO) is responsible for performing recovery of in-doubt
transactions that often occur in distributed transactions.
Check a database is in a
archivelog mode
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. The ARCHIVE LOG LIST command shows
information about the database archive log mode status.
SQL> ARCHIVE LOG LIST
/
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.
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“Education is the
ability to listen to almost anything without losing your temper
or your self confidence.” Robert Frost (1874 - 1963) |
Questions:
Q: What are the Oracle
Background Processes?
Q: Describe the V$BGPROCESS
view.
Q: Describe the following
background processes:
PMON
DBWn
ARC0
CKPT
LGWR
SMON
RECO
Q: Describe an archive log
configuration.
Q: What does the ARCHIVE
LOG LIST command?
Q: What are disadvantage
and advantage of a database in the NOARCHIVELOG mode?
Q: What are disadvantage
and advantage of a database in the ARCHIVELOG mode?
Q: What does the following
SQL statememt?
SQL> SELECT * FROM
v$bgprocess
WHERE PADDR <> '00'
/
Q: How do you test that a
database is in archivelog or not?
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