How to Turn Archiving ON and OFF in Oracle RDBMS [ID 69739.1]

How to Turn Archiving ON and OFF in Oracle RDBMS [ID 69739.1]
		Modified 06-OCT-2011 Type BULLETIN Status PUBLISHED

In this Document
Purpose
Scope and Application
How to Turn Archiving ON and OFF in Oracle RDBMS
Turning Archiving On and Off
Setting the Initial Database Archiving Mode
Changing the Database Archiving Mode
To Prepare to Switch Database Archiving Mode
References

---

Applies to:

Oracle Server - Enterprise Edition - Version: 10.2.0.1 to 11.2.0.2 - Release: 10.2 to 11.2
Information in this document applies to any platform.
***Checked for relevance on 01-Mar-2011***

Purpose

This article gives an overview of database archiving.

In case you may want or need more about your current topic - please also access the Backup & Recover Community of Customers and Oracle Specialists directly via:
https://communities.oracle.com/portal/server.pt/community/database_backup_and_recovery/243

Scope and Application

The intended audience is database administrators.

How to Turn Archiving ON and OFF in Oracle RDBMS

Turning Archiving On and Off

You set a database's initial archiving mode as part of database creation. Usually, you can use the default of NOARCHIVELOG mode at database creation
because there is no need to archive the redo information generated at that time. After creating the database, decide whether to change from the initial archiving mode.

After a database has been created, you can switch the database's archiving mode on demand. However, you should generally not switch the database between archiving modes.

NOTE: If a database is automatically created during Oracle installation, the initial archiving mode of the database is operating system specific. See your operating system-specific Oracle documentation.

ARCHIVELOG mode is necessary for creating on-line backups and for certain types of database recovery. Configuring the database to operate in
ARCHIVELOG mode allows the user to perform complete and point-in-time recovery from media (disk) failures using off-line or on-line backups. If
ARCHIVELOG mode is disabled, the database can be restored from a backup in case of failure, but it cannot be rolled forward from that to a point when failure occurred.

Oracle recommends ARCHIVELOG mode for all production databases

Setting the Initial Database Archiving Mode

When you create the database, you set the initial archiving mode of the redo log in the CREATE DATABASE statement. If you do not specify either ARCHIVELOG or NOARCHIVELOG, NOARCHIVELOG is the default. To verify database mode, execute following statement:

SQL> Select NAME, CREATED, LOG_MODE, CHECKPOINT_CHANGE#, ARCHIVE_CHANGE#
from V$DATABASE

NAME CREATED LOG_MODE CHECKPOINT_CHANGE# ARCHIVE_CHANGE#
--------- --------- ------------ ------------------ ---------------
O112 19-MAR-09 NOARCHIVELOG 1438426 135961

Changing the Database Archiving Mode

There are "init.ora" parameters you need to modify in order to properly handle your database being in archive log mode. They are:

LOG_ARCHIVE_DEST
LOG_ARCHIVE_FORMAT

LOG_ARCHIVE_DEST:
This parameter specifies the directory where your archive logs will be placed.

LOG_ARCHIVE_FORMAT:
This parameter names the archive logs in this format. For example, if your format is: arch%s.arc

Your log files will be called: arch1.arc, arch2.arc, arch3.arc where the '1', '2', '3', etc is the sequence number.

To Prepare to Switch Database Archiving Mode

1. Shut down the database instance.

SQL> shutdown immediate

An open database must be closed and dismounted and any associated instances shut down before the database's archiving mode can be switched. Archiving cannot be disabled if any datafiles need media recovery.

2. Backup the database.

This backup can be used with the archive logs that you will generate.

3. Perform any operating system specific steps (optional).

4. Start up a new instance and mount, but do not open the database.

SQL> startup mount

NOTE: If you are using the Oracle Parallel Server, you must mount the database exclusively using one instance to switch the database's archiving mode.

5. Put the database into archivelog mode

SQL> alter database archivelog; 

NOTE: You can also use

SQL> alter database noarchivelog 

to take the database out of archivelog mode

6. Open the database.

SQL> alter database open; 

7. Verify your database is now in archivelog mode.

SQL> archive log list
Database log mode              Archive Mode
Automatic archival             Enabled
Archive destination            USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence     22
Next log sequence to archive   24
Current log sequence           24

8. Archive all your redo logs at this point.

SQL> archive log all;
 

9. Ensure these newly created Archive log files are added to the backup process.

See the Administration guide & Backup and Recovery guide for more information about switching the archiving mode when using the Oracle Parallel Server.