Project Pxxx - Eurescom - European Institute for Research and

Deliverable 1 Volume 3: Annex 2 - Data manipulation and management issues database. Oracle offers a standby database scheme, with which it maintains a copy of a primary database on duplicate hardware, in a constant recoverable state, by applying the redo logs archived off the primary database.

A full backup is an operating system backup of all of the data files, parameter files, and the control file that constitute the database. A full database backup can be taken by using the operating system’s commands or by using the host command of the

Server Manager. A full database backup can be taken online when the database is open, but only an offline database backup (taken when the database server is shut down) will necessarily be consistent. An inconsistent database backup must be recovered with the online and archived redo log files before the database will become available. The best approach is to take a full database backup after the database has been shut down with normal or immediate priority.

A partial backup is any operating system backup of a part of the full backup, such as selected data files, the control file only, or the data files in a specified tablespace only.

A partial backup is useful if the database is operated in ARCHIVELOG mode. A database operating in NOARCHIVE mode rarely has sufficient information to use a partial backup to restore the database to a consistent state. The archiving mode is usually set during database creation, but it can be reset at a later stage.

You can recover a database damaged by a media failure in one of three ways after you have restored backups of the damaged data files. These steps can be performed using the Server Manager’s Apply Recovery Archives dialog box, using the Server

Manager’s RECOVER command, or using the SQL ALTER DATABASE command:

•

You can recover an entire database using the RECOVER DATABASE command. This command performs media recovery on all of the data files that require redo processing.

•

You can recover specified tablespaces using the RECOVER TABLESPACE command. This command performs media recovery on all of the data files in the listed tablespaces. Oracle requires the database to be open and mounted in order to determine the file names of the tables contained in the tablespace.

•

You can list the individual files to be recovered using the RECOVER

DATAFILE command. The database can be open or closed, provided that Oracle can take the required media recovery locks.

In certain situations, you can also recover a specific damaged data file, even if a backup file isn’t available. This can only be done if all of the required log files are available and the control file contains the name of the damaged file. In addition,

Oracle provides a variety of recovery options for different crash scenarios, including incomplete recovery, change-based, cancel-based, and time-based recovery, and recovery from user errors.

4.2.5

Oracle 8

Oracle 8 offers to the DBA three possibilities for performing backups:

•

Recovery Manager.

•

Operating System.

•

Export.



1999 EURESCOM Participants in Project P817-PF page 103 (120)

Volume 3: Annex 2 - Data manipulation and management issues Deliverable 1

Backup Method

Recovery Manager

Operating System

Export

Version Available

Oracle8

All versions of Oracle

All versions of Oracle

Requirements

Media Manager (if backing up to tape)

O/S backup utility (for example UNIX dd)

N/A

Table 1. Requirements for different backup methods

Summarizing here comes a table wich compares the features of the methods above described.

Feature

closed database backups

Recovery Manager

Supported. Requires instance to be mounted.

open database backups Not use BEGIN/END

BACKUP commands.

Operating System Export

Supported.

Not supported.

Generates more redo when using

BEGIN/END

BACKUP commands

Not supported.

Requires RBS to generate consistent backups.

incremental backups Supported. Backs up all modified blocks.

corrupt block detection Supported. Identifies corrupt blocks and writes to

V$BACKUP_CORRUP

TION or

V$COPY_CORRUPTI

ON.

automatically backs up data

Supported. Establishes the name and locations of all files to be backed up (whole database, tablespace, datafile or control file backup).

catalogs backup performed

Supported. Backups are cataloged to the recovery catalog and to the control file, or just to the control file.

makes backups to tape Supported. Interfaces with a Media Manager.

Not supported.

Not supported.

Not supported.

Files to be backed up must be specified manually.

Not supported.

Supported. Backup to tape is manual or managed by a

Media Manager

Supported.

backs up init.ora and password files

Operating System independent language

An O/S independent scripting language.

O/S dependent.

Supported, but not a true incremental, as it backs up a whole table even if only one block is modified.

Supported. Identifies corrupt blocks in the export log.

Supported. Performes either full, user or table backups.

Not supported.

Supported.

Not supported.

O/S independent scripting language.

Table 2. Feature comparison of backup methods

page 104 (120)



1999 EURESCOM Participants in Project P817-PF