Backup3G/DA-Oracle/User Guide/Defining Oracle Backups

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Revision as of 02:22, 18 April 2006

Oracle backups are configured the same as other backup jobs:

• you define a backup item for each data object to be backed up
• you define backup jobs to back up one or more items at the scheduled time to a particular drive or drive pool

The main differences are:

• in the backup item you use an Oracle-specific backup method instead of one of the standard UNIX methods
• the data object refers to an Oracle SID and not to a filesystem or directory

Note: DA-Oracle does not support the Oracle Parallel Server option.

This section describes the ways you can back up Oracle databases, the Oracle-specific backup methods, and how to define backup items. Defining, scheduling, and monitoring backup jobs is described in the backup3G User Guide.

Types of Oracle Backup

This topic describes the different methods for backing up Oracle databases.

Oracle Backup uses Oracle facilities other than RMAN to start up and shut down databases, and to find the names of objects to be backed up. Once the file names have been obtained, they are backed up the same as any other files using standard backup3G facilities.

What happens if a step fails

If any step in the backup job returns a non-zero exit status, the backup job terminates. In this event DA-Oracle does not try to change the database mode or attempt any other recovery action.

You should diagnose the problem to see whether it occurred in an Oracle operation or a backup command, then if possible fix the problem and resubmit the backup job.

‘Exit status 2’ usually indicates a usage error in the backup command, such as an unrecognized option or an incorrect number of arguments. Other exit statuses are dependent on the backup method—check the manual page for the command that reported the error.

Any previous steps that wrote to the tape and completed successfully may be restored from, but depending on the type of backup may not be worth recovering.

The DBA should examine the reason for failure and the type of object in the successful backup steps to see whether they can be usefully recovered.

Two versions of Oracle installed on a host

The default Oracle version for a host is determined from the Oracle user name specified when DA-Oracle was installed (see Configuring DA-Oracle on page 11). To create a backup item for a database in a non-default copy of Oracle, you specify the other Oracle user name in the Options field of the backup item.

Offline (‘Cold’) Backup

Steps

backup3G performs the following steps when you back up a database using the ‘Oracle offline’ method.

1. Shut down the database.
2. Bring the database back in a restricted mode.
3. Query the database to find the relevant files (control files, redo logs and tablespaces) and store their locations in a COSmanager table.
4. Shut down the database.
5. Back up files.
6. Restart the database.

Notes

The tablespaces are backed up using a multi-part image. The control files and the redo logs are backed up using cpio. ORAofflne follows symbolic links—that is, it backs up the target of any link, not just the link itself.

If the database is online when the backup job starts, DA-Oracle will try to shut it down. If the database cannot be shut down or restarted in restricted mode, the backup job will exit.

By default, DA-Oracle will bring the database back online after an offline backup ends. You can override this in the backup item definition by specifying -d in the Options field.

Online (‘Hot’) Backup

Steps

backup3G performs the following steps when you back up a database or selected tablespaces using the ‘Oracle online’ method.

1. Query the database to find the relevant files (control files, archive logs and tablespaces) and store their locations in a COSmanager table.
2. Put the tablespace into backup mode.
3. Back up the tablespace.
4. Bring the tablespace back online.
5. Repeat steps 2 to 4 for each tablespace.
6. Switch the redo log files to close the backup (as far as Oracle is concerned).
7. Back up the archived redo log files.
8. Back up the control file to a disk file, then back up to tape.

Notes

The database must be run in ARCHIVELOG mode and must be online when the backup job starts. If the database is offline or if DA-Oracle can’t find the location of the relevant files, the backup job will exit.

This provides a complete snapshot of the database or selected tablespaces at the completion of the backup (not the start). Only one tablespace is taken offline and backed up at a time.

The tablespaces are backed up using a multi-part image. The control files and the redo logs are backed up using cpio. ORAofflne follows symbolic links—that is, it backs up the target of any link, not just the link itself.

Archive Log Backup

Steps

1. Query the database to find the redo log files and archive destination.
2. Switch the redo log files to close the backup (as far as Oracle is concerned).
3. Back up the archived redo logs.

Notes

This should be performed frequently (several times per day or hour) from an automatic backup job.

We recommend that you append each days backups to a single media set, to make restores faster and to use tapes more efficiently.

The backup is written in cpio format, so you can restore files from the command line using cpio if necessary.

The database must be online when the backup job starts.

If the redo log files can’t be found (for example if they have already been compressed or removed) the backup job will return exit status 2 and terminate.

Export Backup

Oracle supports three ‘full database’ export modes: complete, cumulative, and incremental. DA-Oracle supports two of these modes: complete and cumulative.

Notes

The database must be online when the backup job starts.

All exports are first written to a temporary file, then this file is backed up using an ‘image’ method.

Defining Oracle Backups

You must define a backup item for each type of backup that you want to perform on a database instance. For example, if the monthly cycle of backups for a particular database includes online and offline backups, backups of archived redo log files, and a complete export, you will need to define four backup items.

Once you have defined all your backup items, you must define a set of backup jobs to back up these items at the scheduled times. See How to Define a Backup Job in the backup3G User Guide.

How to Define a Backup Item

A backup item describes the ‘what’ and ‘how’ of a backup. It identifies the host name and Oracle SID, and the method that will be used to back it up.

How you specify the exact Oracle object to be backed up depends on the backup method.

Each backup method calls a driver script to back up the data. Table 2 shows the backup command and other attributes for each Oracle backup method.

You can use the Options field to pass extra flags and arguments to the backup command. To see what options are supported by each method, check the man page for that driver script.

Note that these options are not validated when you define the backup item, but are simply passed to the backup command to be evaluated at run time.

To define a backup item

1. Select backup3G configuration > Maintain backup jobs.
2. Select Items > Maintain to display the list of existing backup items, then select Maintain > Add.

   Item

   Defaults to one more than the current highest item number. You can change it to any unused item number, but it is recommended that you accept the default.

   Object

   Enter the SID of the instance to be backed up. Make sure that it is correct, as backup3G doesn’t check that it exists at this point.

   Host

   Select the host on which the database is stored. If you want to back up the same database on multiple hosts, you must define a separate backup item for each.

   Method

   Press Choose to list the backup methods.

   Index

   Select ‘yes’ if you chose the ‘Oracle archive’ method. An onlineindex makes it easier to select particular archived redo logs to be restored.

   Options

   Enter any optional flags and arguments to be passed to the backup command at run time. For example, enter -u username to specify another Oracle version if more than one copy of Oracle is installed on this host.

   You can see what other options this backup method supports by checking the man page for the corresponding backup driver script. Table 2 shows what driver script is run by each Oracle backup method.

   Note - Use double quotes around file patterns to ensure that they are parsed correctly.

   Comment

   Enter a descriptive comment.

   On error

   Should the backup job continue if this step fails?

3. Select ‘continue’ if the job should continue after an error in this step.
4. Select ‘abort’ if the job should not continue.
5. Press Accept to save this item.