Oracle® Database
Backup and Recovery Basics
10g Release 1 (10.1)
Part No. B10735-01
December 2003
Oracle Database Backup and Recovery Basics 10g Release 1 (10.1)
Part No. B10735-01
Copyright © 2003 Oracle Corporation. All rights reserved.
Primary Author: Antonio Romero
Contributing Author: Lance Ashdown
Contributors: Anand Beldalker, Tammy Bednar, Don Beusee, Senad Dizdar, Wei Hu, Donna Keesling,
Bill Lee, Muthu Olagappan, Francisco Sanchez, Vinay Srihari, Steve Wertheimer
Graphic Artist: Valarie Moore
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Complete, Incomplete and Point-In-Time Recovery............................................................. 1-10
Automatic Recovery After Instance Failure: Crash Recovery ............................................. 1-11
Backup and Recovery with RMAN............................................................................................... 1-12
Types of Oracle Database Backup under RMAN .................................................................. 1-12
Matching Failures to Backup and Recovery Techniques.......................................................... 1-14
iv
Media Failure............................................................................................................................... 1-14
User Error..................................................................................................................................... 1-16
Automatic Disk-Based Backup and Recovery: The Flash Recovery Area ............................. 1-16
System Requirements for Backup and Recovery Methods ...................................................... 1-17
Feature Comparison of Backup Methods..................................................................................... 1-18
2 Backup and Recovery Strategies
Data Recovery Strategy Determines Backup Strategy................................................................. 2-2
Planning Data Recovery Strategy .................................................................................................... 2-5
Planning a Response to User Error: Point-in-Time Recovery and Flashback Features...... 2-5
Planning a Response to Media Failure: Restore and Media Recovery ................................. 2-6
Planning a Response to Datafile Block Corruption: Block Media Recovery........................ 2-7
Planning Backup Strategy................................................................................................................. 2-8
Protecting Your Redundancy Set ............................................................................................... 2-8
Deciding Between ARCHIVELOG and NOARCHIVELOG Mode..................................... 2-10
Deciding Whether to Use a Flash Recovery Area.................................................................. 2-11
Choosing a Backup Retention Policy....................................................................................... 2-12
Archiving Older Backups .......................................................................................................... 2-14
Determining Backup Frequency............................................................................................... 2-14
Performing Backups Before and After You Make Structural Changes............................... 2-15
Backing Up Frequently Used Tablespaces.............................................................................. 2-15
Backing Up after NOLOGGING Operations.......................................................................... 2-16
Exporting Data for Added Protection and Flexibility........................................................... 2-16
Preventing the Backup of Online Redo Logs.......................................................................... 2-17
Keeping Records of the Hardware and Software Configuration of the Server................. 2-17

Overview of RMAN Backups........................................................................................................... 4-2
Files That RMAN Can Back Up.................................................................................................. 4-2
RMAN Backup Formats: Image Copies and Backup Sets ...................................................... 4-3
Full and Incremental Datafile Backups ..................................................................................... 4-5
RMAN Backups and Tags ........................................................................................................... 4-5
Backing Up Database Files and Archived Logs with RMAN .................................................... 4-5
Making Consistent and Inconsistent Backups with RMAN .................................................. 4-6
Making Whole Database Backups with RMAN....................................................................... 4-6
Backing Up Individual Tablespaces with RMAN ................................................................... 4-7
Backing Up Datafiles and Datafile Copies with RMAN........................................................ 4-8
Backing Up Control Files with RMAN...................................................................................... 4-9
Backing Up Server Parameter Files with RMAN................................................................... 4-10
Backing Up Archived Redo Logs with RMAN...................................................................... 4-10
Using Compressed Backupsets................................................................................................. 4-12
vi
RMAN Incremental Backups.......................................................................................................... 4-13
Making Incremental Backups: BACKUP INCREMENTAL .............................................. 4-19
Incrementally Updated Backups: Rolling Forward Image Copy Backups ........................ 4-20
Improving Incremental Backup Performance: Change Tracking........................................ 4-23
Backing Up to the Flash Recovery Area: Basic Scenarios ......................................................... 4-25
Scripting Disk-Only Backups.................................................................................................... 4-26
Backing Up to the Flash Recovery Area and to Tape: Basic Scenarios................................... 4-32
Configuring the RMAN Environment for Disk and Tape Backups.................................... 4-33
Writing Backup Scripts for Disk and Tape Scenarios............................................................ 4-33
Validating RMAN Backups............................................................................................................. 4-42
Overview of Querying the RMAN Repository........................................................................... 4-43
Listing RMAN Backups, Archived Logs, and Database Incarnations.................................... 4-44
About RMAN Lists..................................................................................................................... 4-44
Listing Backups........................................................................................................................... 4-45
Listing Backups in Summary Mode......................................................................................... 4-48

Maintaining the RMAN Repository in the Control File............................................................. 6-5
Crosschecking Backups ............................................................................................................... 6-5
Deleting Backups.......................................................................................................................... 6-7
Crosschecking and Deleting on Multiple RMAN Channels ................................................... 6-11
About Allocating Multiple RMAN Channels for Maintenance Commands ..................... 6-11
How RMAN Crosschecks and Deletes on Multiple Channels ............................................ 6-11
Crosschecking Disk and Tape Channels with One Command: Example .......................... 6-12
Crosschecking on Multiple Oracle Real Application Cluster Nodes: Example ................ 6-13
Deleting on Disk and Tape Channels with One DELETE Command: Example............... 6-13
Releasing Multiple Channels: Example................................................................................... 6-15
Deleting a Database with RMAN............................................................................................. 6-15
Changing the Status of a Backup Record..................................................................................... 6-16
Marking a Backup AVAILABLE or UNAVAILABLE........................................................... 6-16
Exempting a Backup from the Retention Policy .................................................................... 6-17
Cataloging Archived Logs and User-Managed Copies ............................................................. 6-17
About Cataloging Archived Logs and User-Managed Copies............................................ 6-18
Cataloging User-Managed Datafile Copies ............................................................................ 6-19
Cataloging Backup Pieces.......................................................................................................... 6-19
Cataloging All Files in a Disk Location................................................................................... 6-20
Uncataloging RMAN Records........................................................................................................ 6-21
About Uncataloging RMAN Records...................................................................................... 6-21
Removing Records for Files Deleted with Operating System Utilities............................... 6-21
Flash Recovery Area Maintenance ................................................................................................ 6-22
Resolving a Full Flash Recovery Area..................................................................................... 6-22
viii
Changing the Flash Recovery Area to a New Location ........................................................ 6-23
Flash Recovery Area Behavior When Instance Crashes During File Creation.................. 6-23
Glossary
Index
ix

tronic mail address.
If you have problems with the software, please contact your local Oracle Support Services.
x
xi
Preface
This guide provides a basic conceptual overview of Oracle database backup and
recovery.
This preface contains these topics:
■
Audience
■
Organization
■
Related Documentation
■
Conventions
■
Documentation Accessibility
xii
Audience
This manual is intended for database administrators who perform backup and
recovery of an Oracle database server.
To use this document, you need to know the following:
■
Relational database concepts and basic database administration as described in
Oracle Database Concepts and Oracle Database Administrator's Guide
■
The operating system environment under which you are running the Oracle
database
Organization

Many of the examples in this book use the sample schemas of the seed database,
which is installed by default when you install Oracle. Refer to Oracle Database
Sample Schemas for information on how these schemas were created and how you
can use them yourself.
Printed documentation is available for sale in the Oracle Store at
/>To download free release notes, installation documentation, white papers, or other
collateral, please visit the Oracle Technology Network (OTN). You must register
online before using OTN; registration is free and can be done at
/>If you already have a username and password for OTN, then you can go directly to
the documentation section of the OTN Web site at
m/documentation/
Conventions
This section describes the conventions used in the text and code examples of this
documentation set. It describes:
■
Conventions in Text
■
Conventions in Code Examples
Conventions in Text
We use various conventions in text to help you more quickly identify special terms.
The following table describes those conventions and provides examples of their use.
xiv
Conventions in Code Examples
Code examples illustrate SQL, PL/SQL, SQL*Plus, or other command-line
statements. They are displayed in a monospace (fixed-width) font and separated
from normal text as shown in this example:
SELECT username FROM dba_users WHERE username = 'MIGRATE';
Convention Meaning Example
Bold Bold typeface indicates terms that are
defined in the text or terms that appear in

monospace
(fixed-width)
font
Lowercase monospace typeface indicates
executables, filenames, directory names,
and sample user-supplied elements. Such
elements include computer and database
names, net service names, and connect
identifiers, as well as user-supplied
database objects and structures, column
names, packages and classes, usernames
and roles, program units, and parameter
values.
Note: Some programmatic elements use a
mixture of UPPERCASE and lowercase.
Enter these elements as shown.
Enter sqlplus to open SQL*Plus.
The password is specified in the orapwd file.
Back up the datafiles and control files in the
/disk1/oracle/dbs directory.
The department_id, department_name, and
location_id columns are in the
hr.departments table.
SettheQUERY_REWRITE_ENABLEDinitialization
parameter to true.
Connect as oe user.
The JRepUtil class implements these methods.
lowercase
italic
monospace

■
That we have omitted parts of the
code that are not directly related to
the example
■
That you can repeat a portion of the
code
CREATE TABLE ... AS subquery;
SELECT col1, col2, ... , coln FROM
employees;
.
.
.
Vertical ellipsis points indicate that we
have omitted several lines of code not
directly related to the example.
SQL> SELECT NAME FROM V$DATAFILE;
NAME
------------------------------------
/fsl/dbs/tbs_01.dbf
/fs1/dbs/tbs_02.dbf
.
.
.
/fsl/dbs/tbs_09.dbf
9 rows selected.
Other notation You must enter symbols other than
brackets, braces, vertical bars, and ellipsis
points as shown.
acctbal NUMBER(11,2);

terms in uppercase in order to distinguish
them from terms you define. Unless terms
appear in brackets, enter them in the
order and with the spelling shown.
However, because these terms are not
case sensitive, you can enter them in
lowercase.
SELECT last_name, employee_id FROM
employees;
SELECT * FROM USER_TABLES;
DROP TABLE hr.employees;
lowercase
Lowercase typeface indicates
programmatic elements that you supply.
For example, lowercase indicates names
of tables, columns, or files.
Note: Some programmatic elements use a
mixture of UPPERCASE and lowercase.
Enter these elements as shown.
SELECT last_name, employee_id FROM
employees;
sqlplus hr/hr
CREATE USER mjones IDENTIFIED BY ty3MU9;
Convention Meaning Example
xvii
that Oracle does not own or control. Oracle neither evaluates nor makes any
representations regarding the accessibility of these Web sites.
xviii
Backup and Recovery Overview 1-1
1

Physical Backups and Logical Backups
A backup is a copy of data from your database that can be used to reconstruct that
data. Backups can be divided into physical backups and logical backups.
Physical backups are backups of the physical files used in storing and recovering
your database, such as datafiles, control files, and archived redo logs. Ultimately,
every physical backup is a copy of files storing database information to some other
location, whether on disk or some offline storage such as tape.
Logical backups contain logical data (for example, tables or stored procedures)
exported from a database with an Oracle export utility and stored in a binary file,
for later re-importing into a database using the corresponding Oracle import utility..
Physical backups are the foundation of any sound backup and recovery strategy.
Logical backups are a useful supplement to physical backups in many
circumstances but are not sufficient protection against data loss without physical
backups.
Unless otherwise specified, the term "backup" as used in the backup and recovery
documentation refers to physical backups, and to backup part or all of your
database is to take some kind of physcial backup. The focus in the backup and
recovery documentation set will be almost exclusively on physical backups.
Errors and Failures Requiring Recovery from Backup
While there are several types of problem that can halt the normal operation of an
Oracle database or affect database I/O operations, only two typically require DBA
intervention and media recovery: media failure, and user errors.
Other failures may require DBA intervention to restart the database (after an
instance failure) or allocate more disk space (after statement failure due to, for
instance, a full datafile) but these situations will not generally cause data loss or
require recovery from backup.
See also:
Oracle Database Utilities for more details about
importing and exporting data using Oracle export and import
utilities.

user-managed methods more easily, provides a common interface for backup tasks
across different host operating systems, and offers a number of backup techniques
not available through user-managed methods.
Most of the backup and recovery documentation set will focus on RMAN-based
backup and recovery. User-managed backup and recovery techniques are covered
in the later chapters of Oracle Database Backup and Recovery Advanced User's Guide.
Whether you use RMAN or user-managed methods, you can supplement your
physical backups with logical backups of schema objects made using data export
What is Backup and Recovery?
1-4 Backup and Recovery Basics
utilities. Data thus saved can later be imported to re-create this data after restore
and recovery. However, logical backups are for the most part beyond the scope of
the backup and recovery documentation.
Backup and Recovery: Basic Concepts
Backup and Recovery Overview 1-5
Backup and Recovery: Basic Concepts
The physical structures of the database and the role each plays in the database
recovery process are what determine the forms of backup and recovery available
through user-managed techniques and through RMAN.
Physical Database Structures Used in Recovering Data
The files and other structures that make up an Oracle database store data and
safeguard it against possible failures. This section introduces each of the physical
structures that make up an Oracle database and their role in the reconstruction of a
database from backup. This section contains these topics:
■
Datafiles and Data Blocks
■
Redo Logs
■
Undo Segments

An Oracle database requires at least two online redo log groups, and in each group
there is at least one online redo log member, an individual redo log file where the
changes are recorded.
At intervals, the database rotates through the online redo log groups, storing
changes in the current online redo log while the groups not in use can be copied to
an archive location, where they are called archived redo logs (or, collectively, the
archived redo log). You can run your database in ARCHIVELOG mode (in which
this archiving of redo log files is enabled) or NOARCHIVELOG mode (in which
redo log files are simply overwritten).
Preserving the archived redo log is a major part of most backup strategies, as they
contain a record of all updates to datafiles. Backup strategies often involve copying
the archived redo logs to disk or tape for longer-term storage. Running in
NOARCHIVELOG mode limits your data recovery options.
Control Files
The control file contains a crucial record of the physical structures of the database
and their status. Several types of information stored in the control file are related to
backup and recovery:
■
Database information (RESETLOGS SCN and time stamp)
■
Tablespace and datafile records (filenames, datafile checkpoints, read/write
status, offline ranges)
■
Information about redo threads (current online redo log)
■
Log records (log sequence numbers, SCN range in each log)
■
A record of past RMAN backups
See also:
Oracle Database Administrator's Guide for more details

database server.
To recover a datafile (also called performing recovery on a datafile), is to take a
restored copy of the datafile and apply to it changes recorded in the database's redo
logs. To recover a whole database is to perform recovery on each of its datafiles.
Figure 1–1 illustrates the basic principle of backing up, restoring, and recovering a
database. Most of the data recovery procedures supported by the Oracle database
are variations on the process described here.
See also:
Oracle Database Concepts for more information about
control files.
See also:
Oracle Database Concepts for detailed information about
undo segements.