Configuring RMAN for Use

RMAN will work out of the box without any configuration. Unfortunately, this is generally not a good idea. RMAN tends to throw things into ORACLE_HOME if you have not configured the database and RMAN correctly. In this section, we will address configuring RMAN correctly.

In the following sections, we will introduce you to the flash recovery area (FRA) in RMAN. We will then address RMAN persistent configuration settings to allow for streamlined backups followed by using nonpersistent settings when required. Finally, we will cover configuring RMAN for its first use.

The Flash Recovery Area

The Oracle flash recovery area (FRA) was introduced in Oracle Database 10g as the central repository for all files related to Oracle backup and recovery. In this section, we will discuss the flash recovery area. First we will have a quick overview of what the FRA is generally used for. Then you’ll learn about configuring the FRA for your Oracle database.

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Introducing the FRA

The FRA is the principal store for all Oracle database backup–related files. The FRA can be stored on disk or within an ASM instance. It cannot be stored on tape, but files backed up in the FRA can be backed up to tape via the RMAN backup recovery area command.

The FRA stores the following types of Oracle database files:

The FRA supports RMAN’s backup and retention policies by automatically removing files when they are no longer needed and when FRA space is required (obsolete RMAN backups to non-FRA locations will not be removed by RMAN automatically).

Configuring the FRA

Configuring the FRA is easy. First you create the base directory of the FRA from the OS, and then you set the following parameters in any database that will use the FRA:

NN DB_RECOVERY_FILE_DEST

NN DB_RECOVERY_FILE_DEST_SIZE

The DB_RECOVERY_FILE_DEST parameter defines the FRA base directory location. This is the only directory you will need to create when configuring the FRA. You will need to

make sure that this directory is owned by the owner of the Oracle executable so that Oracle can create other subdirectories beneath it.

The DB_RECOVERY_FILE_DEST_SIZE parameter defines the total amount of space for this database instance is allowed to consume in the FRA. This is a logical limit, which can be greater than or less than the actual physical limit of space on that device. For example, you may have a file system with 500GB of space available on it. However, you may want to indicate that your database can consume only up to 100GB of space within the FRA while assigning the FRA to the 500GB file system.

You use the alter system command to configure the FRA. Note that DB_RECOVERY_ FILE_DEST is not dynamic, while DB_RECOVERY_FILE_DEST_SIZE is dynamic. To configure the FRA, do the following:

1.Create the base FRA directory:

/u01>mkdir /oracle01/fra

2.Log into SQL*Plus:

C:\oracle\orabackup\orcl>sqlplus sys as sysdba

SQL*Plus: Release 11.1.0.6.0 - Production on Thu Aug 14 18:57:13 2008 Copyright (c) 1982, 2007, Oracle. All rights reserved.

Enter password: Connected to:

Oracle Database 11g Enterprise Edition Release 11.1.0.6.0 - Production With the Partitioning, OLAP, Data Mining and Real Application

Testing options SQL>

3.Now use the alter system command to set the parameter DB_RECOVERY_FILE_DEST to

/oracle01/fra and DB_RECOVERY_FILE_DEST_SIZE to 2GB.

sql>alter system set db_recovery_file_dest_size=2GB;

sql>alter system set db_recovery_file_dest=’/oracle01/fra’ scope=spfile;

4.Now shut down and restart the database. Once the database has been restarted, the FRA will become operational.

Managing the FRA

Management of the FRA is done principally by Oracle based on backup retention settings for RMAN (see the section “Retention Policies” later in this chapter). Thus, as backups become obsolete and as FRA space is exhausted by an instance, Oracle will remove those obsolete backups automatically. As a result, over time FRA space tends to reach an equilibrium, assuming that the database datafiles do not grow at a great rate.

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Really Using the FRA

In the real world, it’s hard to get things right the first time. Using the FRA is no exception. One of us had a client that had a few problems when they first switched to using the FRA. The databases were not set up correctly, so the FRA would fill up.

Over time, the FRA became more stable as we understood the load profile and its relationship to the creation of archived redo logs and backups. We eventually found the sweet spot with respect to how much disk space we needed to allocate to the FRA. This is actually a good thing because it forced them to realize that understanding the disk-usage profile of their databases was important.

Monitoring of the FRA is another real-world issue to be aware of. Many companies that are using the FRA are investing some time in scripts to monitor FRA disk-space usage. OEM can be used for this too.

The FRA does require some care and feeding by the DBA, however, particularly at first. Sometimes it’s hard to properly estimate the correct setting for the DB_RECOVERY_FILE_ DEST_SIZE and you will find the FRA filling up. Archived redo logs are stored in the FRA, so if the FRA fills up, archived redo logs will no longer be able to be written.

If this occurs, Oracle will first try to free space in the FRA by removing obsolete backups. If Oracle cannot free up enough space, then eventually the inability to archive will cause the database to freeze until the out-of-space condition can be rectified. In this case, you can free up space by changing DB_RECOVERY_FILE_DEST_SIZE to a higher value. This parameter is dynamic, so the change can be made immediately.

You can use the V$DB_RECOVERY_FILE_DEST view to determine the state of the FRA. In the following example, we find that the FRA is sized to 2GB and that we have used 251MB in total. We also see that 41MB of that space is reclaimable. In short, this FRA looks pretty good at this point.

If you manually remove files from the FRA, you will have to let Oracle know that you have done so. By default Oracle will not detect that the files have been removed. Oracle can detect the file removals by using the RMAN crosscheck and delete expired commands. See Chapter 7 for more information on using these commands.

RMAN Persistent Configuration Settings

When RMAN first came out in Oracle version 8.0, you had to manually indicate in each backup where the backup destination was to be, any limits related to the backup (such as the maximum size of backup set pieces), and so on. This required a lot of work and made RMAN a bit more archaic-looking and difficult to use.

Oracle Database version 9i introduced the concept of persistent configuration in RMAN. RMAN persistent configuration settings are settings that are configured through the RMAN interface, stored in the control file, and automatically used during each backup unless they are overridden.

Oracle Database 11g provides for a number of persistent settings, including the following:

You can see the current settings for all persistent parameters in RMAN by using the RMAN show all command, as shown here:

RMAN> show all;

using target database control file instead of recovery catalog

RMAN configuration parameters for database with db_unique_name ORCL are: CONFIGURE RETENTION POLICY TO REDUNDANCY 1; # default

CONFIGURE BACKUP OPTIMIZATION OFF; # default CONFIGURE DEFAULT DEVICE TYPE TO DISK; # default CONFIGURE CONTROLFILE AUTOBACKUP OFF; # default

CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO ‘%F’; #default CONFIGURE DEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO BACKUPSET; # default CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default CONFIGURE ARCHIVELOG BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default CONFIGURE CHANNEL DEVICE TYPE DISK MAXPIECESIZE 100 M;

CONFIGURE MAXSETSIZE TO UNLIMITED; # default CONFIGURE ENCRYPTION FOR DATABASE OFF; # default CONFIGURE ENCRYPTION ALGORITHM ‘AES128’; # default CONFIGURE COMPRESSION ALGORITHM ‘BZIP2’; # default

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CONFIGURE ARCHIVELOG DELETION POLICY TO NONE; # default CONFIGURE SNAPSHOT CONTROLFILE NAME TO ‘C:\ORACLE\PRODUCT\11.1.0\DB_1\DATABASE\SNCFORCL.ORA’; # default

You can also look at an individual setting by using the show command followed by the setting you are interested in. In this example, we are interested in the retention policy:

RMAN> show retention policy;

RMAN configuration parameters for database with db_unique_name ORCL are: CONFIGURE RETENTION POLICY TO REDUNDANCY 1; # default

You can clear configuration settings using the configure clear command, as shown in this example:

RMAN>configure device type disk clear;

Unique RMAN Configuration Settings

Sometimes you need to do something different. Perhaps you have configured your default channels to go to tape but you want a particular backup to go to disk one time. You can configure unique one-time-only settings in RMAN through the use of a combination of the set command, a run block, and individual keywords available in specific commands. Here is an example of using a run block to override channel defaults. We also use the allocate channel command to manually allocate channels:

run {

allocate channel c1 device type disk format ’c:\oracle\oraback1\orcl\%U’; allocate channel c2 device type disk format ’c:\oracle\oraback2\orcl\%U’; backup database plus archivelog;

};

You can also use options within the backup command to override default settings. For example, by default RMAN will write backups to the FRA, so the backup command (which we will discuss later in this chapter) is as simple as backup database plus archivelog. If you want to write to a directory other than the FRA for a single backup, you would include the format keyword to override the default setting, as in

this example:

backup database format ’c:\oracle\backup\backup\%U.bak’ plus archivelog format ’c:\oracle\backup\arch\%U.bak’;

The RMAN Backup and Recovery Manuals

Oracle provides some great sources of information within the Oracle documentation set. We strongly recommend you acquaint yourself with the Oracle documentation and especially the Oracle RMAN documentation. The place to go for the online Oracle documentation is http://tahiti.oracle.com. For RMAN backup and recovery, look at the following books while you are preparing for your OCP exam:

And finally, if we may pat our own backs a little bit, a great book on getting to know RMAN is Oracle Database 10g RMAN Backup & Recovery by Robert G. Freeman and Matthew Hart (Oracle Press/McGraw-Hill, 2007). It’s a comprehensive guide to all things RMAN. The Oracle Database 11g version should be available sometime in 2009.

Preparing RMAN for Use

Before you use RMAN, you will want to customize it to use your preferences. This makes the backup process easy and repeatable with a minimum of effort. In this section, we will discuss a number of configurable features of RMAN:

Let’s look at each of these in some more detail.

Setting the control_file_record_keep_time Parameter

When using RMAN without a recovery catalog (which we discuss in Chapter 5), you will need to make sure that you have set the CONTROL_FILE_RECORD_KEEP_TIME parameter correctly. This parameter is used to determine how long RMAN-related control-file records are maintained in the control file. Make sure this parameter is set high enough so that it will not interfere with your retention-policy requirements (see the next section for more on retention policies).

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command to list those backups subject to removal based on the retention policy and then use the delete obsolete command to remove those backups. Here is an example:

RMAN> report obsolete;

RMAN retention policy will be applied to the command

\BACKUPSET\2008_09_07\O1_MF_ANNNN_TAG20080907T170612_4D8QMNYR_.BKP RMAN> delete noprompt obsolete;

RMAN retention policy will be applied to the command

\BACKUPSET\2008_09_07\O1_MF_ANNNN_TAG20080907T170612_4D8QMNYR_.BKP deleted backup piece

backup piece handle=C:\ORACLE\BACKUP\0MJPS3LL_3_1.ORCL RECID=36 STAMP=664670185

deleted backup piece

backup piece handle=C:\ORACLE\BACKUP\0MJPS3LL_2_1.ORCL RECID=35 STAMP=664670069

deleted backup piece

backup piece handle=C:\ORACLE\BACKUP\0MJPS3LL_1_1.ORCL RECID=34 STAMP=664669886

deleted backup piece

backup piece handle=C:\ORACLE\BACKUP\0NJPS3VG_1_1.ORCL RECID=37 STAMP=664670208

deleted backup piece

backup piece handle=C:\ORACLE\BACKUP\0OJPS402_1_1.ORCL RECID=38 STAMP=664670216

deleted backup piece

backup piece handle=C:\ORACLE\FLASH_RECOVERY_AREA\ORCL \BACKUPSET\2008_09_07\O1_MF_ANNNN_TAG20080907T170612_4D8QMNYR_.BKP RECID=39 STAMP=664823188

Deleted 6 objects

Using the Keep Option

If you have a defined retention policy, you may well want to override it for specific backups. Perhaps you have a policy that says at the end of the year you will make a backup of the database and keep it forever, or perhaps you have a “gold” copy backup that you want to keep for a longer period of time than the default retention policy allows. The keep option provides the ability to override the default retention policy. You can define a different retention policy for the specific backup (for example, remove it in 180 days) or you can choose to keep the backup until you decide to obsolete it manually with the unkeep command.

For example, if you wanted to create a backup with a retention criterion of 365 days, you would issue the following command:

RMAN> backup database plus archivelog delete input keep until time ‘sysdate + 365’;

Using the keep forever option, you could keep the backup indefinitely, as shown here:

RMAN> backup database plus archivelog tag=gold_copy delete input keep forever;

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Note that the use of the keep option does not require that you back up archived redo logs at the same time. Issuing the keep command will cause RMAN to back up the archived redo logs needed to restore the backup you are indicating you want to keep. So you could avoid the plus archivelog option if you wanted, as shown here:

RMAN> backup database format ‘c:\oracle\backup\%U’

keep until time “sysdate+300” tag=’DavidW_HeberA_BillJ_JedB_DanD_MandyC’;

The keep forever option requires that you use a recovery catalog. The keep until time option does not require the use of a recovery catalog.

You can use the change command to subsequently decide to keep a backup or to change the setting on a backup so that the status of the backup is no longer set to keep. For example, you can take a backup with a tag of gold_backup that was backed up with the keep command and start to enforce the retention criteria on that backup by using the change nokeep command, as shown here:

RMAN>backup database plus archivelog tag=gold_copy delete input format ‘c:\oracle\backup\%U’ keep until time “sysdate+300”;

RMAN>change backupset tag gold_backup nokeep;

You cannot create backups on which you’ve used the keep option in the FRA. If you want to create backups that have nonstandard retention criteria, you will have to use a non-FRA location to create them. This often requires the use of the format parameter, as shown in this example:

backup database format ’c:\oracle\backup\%U’ keep until time ”sysdate+300” ;

Configuring Retention Policies

Retention policies are configured in RMAN using the configure command. When configuring a redundancy configuration policy, you will use the configure command with the retention policy to redundancy keywords, as shown here:

RMAN> configure retention policy to redundancy 1 ;

To configure a recovery-window retention policy, you use the configure command with the retention policy to recovery window of days keywords, as shown here:

RMAN> configure retention policy to recovery window of 2 days;

To disable the retention policy, use the configure command with the retention policy to none keywords, as shown here:

RMAN> configure retention policy to none;

Compression

RMAN has long offered white-space compression. Essentially, this means that blocks in a datafile that are not used do not get backed up. White-space compression is quite helpful for a database that is sized quite large but contains little data. It is less helpful for wellpacked databases.

In these cases, you will want to take advantage of actual backup set compression. This is compression not unlike that available with operating system programs like pkzip, gzip, and compress. Oracle Database 11g offers two flavors of compression, zlib and bzip2 (the default). Zlib is designed to compress with a minimum of CPU impact. The result is often a slightly bigger backup image than you get with the bzip2 compression format.

You can configure compression as a default value with the configure compression algorithm command followed by the compression format name, as shown in this example:

RMAN> configure compression algorithm ‘zlib’;

To actually perform a backup with compression, you will need to configure the default device type to use compression, or you will have to use the as compressed keyword when issuing the backup command. Here is an example of configuring the default device type to use compression:

RMAN> configure device type disk backup type to compressed backupset;

And here is an example of using the as compressed keyword when creating a backup: backup as compressed backupset database plus archivelog;

The Hidden Talents of Compression

Sometimes there’s a product feature that has hidden benefits. Compression is one of these. While compression can help reduce the size of your backup sets, there is another potential feature that we look at in the real world, and that is an overall reduction in I/O. With compression enabled, we often see a reduction in backup and recovery times since there is less disk I/O associated with the backup. This can result in reduced backup times, and the backups may have less impact on the overall system.

Everything comes with a price, though, and in this case it’s CPU. Compression comes with a high CPU cost. On systems where there was plenty of CPU to go around, we have seen compression significantly reduce backup times and I/O impacts.

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Encryption

You can choose to encrypt your backups in Oracle Database 11g. Several encryption options are available to you, and they can be found by querying the V$RMAN_ENCRYPTION_ALGORITHMS view. You can use the configure command to define the default level of encryption that you want to use. You then use the configure command to enable encryption for the entire database or for specific tablespaces.

For example, if you wanted to configure encryption for the entire database, you would use the following commands:

RMAN> configure encryption algorithm “AES128”;

RMAN> configure encryption for database on;

Encryption options for a given tablespace will take precedence over the database global settings. Thus, you can enable global encryption for the database and disable it for a specific tablespace.

There are three different modes of encryption (as opposed to the algorithm used). These are transparent mode, password-based encryption, and dual-mode encryption, which encompasses both modes of encryption. For transparent encryption, you will need to create a wallet, and it must be open. Transparent encryption will then occur automatically after you have issued the configure encryption for database on or configure encryption for tablespace on command.

For password authentication, you will need to use the set encryption identified by command first to enable password-based authentication. If you are restoring you will have to use the set decryption identified by command to set the password to decrypt a backup. You can also use the set command to change the type of encryption for a specific backup or to turn off encryption. Here is an example of the use of the set encryption command:

RMAN> set encryption identified by my_pass only on for all tablespaces;

Channel Configuration

When you initiate an RMAN backup, RMAN will create one or more channels that connect the database to a backup device. By default, RMAN will create a single channel to back up or recover to or from the FRA. You can override the defaults using the configure command. Along with backup locations, the configure command allows you to define other settings for your backup channels, including parallelism and backup-set and piece-set sizing. In the following sections, you’ll learn about using the configure command to define default backup locations, about configuring parallelism, and then about using the configure command to set other channel-related parameters.

Configuring Backup Locations

The configure default device command is used to configure a backup location other than the default location. If, for example, you wanted to back up to a directory called /oracle01/ backup/orcl, you would issue the following command:

RMAN> configure channel device type disk format ‘/oracle01/backup/orcl/%U’;

RMAN will use this path for future backups. You can configure multiple channels with the configure command by specifying each individual channel, as shown here where we have indicated different default backup locations for each channel:

RMAN> configure channel 1 device type disk format ‘/oracle01/backup/orcl/%U’; RMAN> configure channel 2 device type disk FORMAT ‘/oracle02/backup/orcl/%U’;

You might have wondered about the %U in the backup location format. The %U is an RMAN backup format specification. There are a number of different format specifications. %U is

the most common because it ensures a unique filename for each backup set piece created by RMAN. Table 4.2 provides a list of the most common format specifications.

Ta b l e 4 . 2   ​  Format​ Options

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anytime a database change occurs that impacts the control file and the database physical structure, such as adding a tablespace or datafile.

To enable control-file autobackups through RMAN, use the configure command with the controlfile autobackup on keyword, as shown here:

RMAN> configure controlfile autobackup on;

Control-file autobackups are stored in the FRA if one is configured. You can also use the configure command to configure RMAN to create the control-file autobackup in a different location, as shown in this example:

configure controlfile autobackup format for device type disk to ‘/oracle01/oracle/controfilebackup/%F’;

In this example, notice the use of the %F format specifier. %F is required when defining the location of the backup control file. This will ensure that the backup control file name is unique each time the backup is created.

Backup Optimization

Sometimes things don’t change, like some of our T-shirts (they are older than we are!) and read-only datafiles. When this happens, you don’t need to back them up if they have already been backed up. Backup optimization provides the ability to tell RMAN that you don’t want to back up a database datafile if that backup is not needed. This saves time and effort on the part of RMAN. RMAN still follows all the rules of retention, backup files are expired when they are set to expire, and if the retention policy calls for two copies of a

datafile, then the datafile will be backed up two times. However, on the third backup of the database, the read-only datafile will not be backed up, because the two identical copies are sufficient for recovery.

To configure backup optimization, use the configure command with the backup optimization on keyword, as shown here:

RMAN> configure backup optimization on;

Snapshot Control-File Location

As we mentioned earlier, Oracle places the snapshot control file in the ORACLE_HOME/dbs directory. As a part of the setup of RMAN, you should change the location of the snapshot control file by using the configure command, as shown here:

configure snapshot controlfile name to ’/oracle01/backup/sncf/sncforcl.ora’;

Backup Tags

When you create backups, you can optionally tag them. If you do not tag a backup, RMAN will tag it for you. A tag is a name that you assign to the backup, such as, for example, Gold Copy (perhaps you re-create your database every day with the backup tagged Gold Copy).

You can easily restore and recover the database using the tag as the key for the recovery. We will discuss using tags to recover your database in Chapter 6. Here is an example of performing a backup with a tag included:

RMAN> backup database tag ‘DPrestwich’ plus archivelog tag=’ARCH_GOLD’ delete input;

Duplexing Backups

You may want to create duplicate copies of backup sets when they are created. This is called duplexing. Duplexing of backup sets can be configured as a default setting by using the configure command, as shown here:

RMAN>configure datafile backup copies for device type disk to 2;

You can also configure duplexing for archive log backups, as shown here:

RMAN>configure archivelog backup copies for device type disk to 2;

Note that you can duplex across similar devices only. So you can duplex across tape devices or across disk devices but not both.

If you want to duplex an individual backup rather than set a persistent configuration setting, you would use the set backup copies command within a RUN block, as in this example:

RMAN> run 2> {

3> allocate channel d1 device type disk format ‘c:\oracle\backup\%U’; 4> set backup copies 2;

5> backup incremental level 0 database plus archivelog delete input; 6> }

In Exercise 4.1, you’ll configure some RMAN settings.

E x e r c i s e 4 .1

Configuring RMAN

1.Start RMAN from the command line:

C:\oracle\admin\ORCL\wallet>rman target=/ Recovery Manager: Release 11.1.0.6.0 - Production

178  Chapter 4  n  Configuring and Backing Up Using RMAN

E x e r c i s e 4 .1   ( c o nt i n u e d )

on Thu Sep 11 18:28:24 2008

Copyright (c) 1982, 2007, Oracle. All rights reserved. connected to target database: ORCL (DBID=1190537904)

2.Display your RMAN configuration (yours may look different than our output— that’s okay):

RMAN> show all;

RMAN configuration parameters for database with db_unique_name ORCL are: CONFIGURE RETENTION POLICY TO REDUNDANCY 1;

CONFIGURE BACKUP OPTIMIZATION ON;

CONFIGURE DEFAULT DEVICE TYPE TO DISK; # default CONFIGURE CONTROLFILE AUTOBACKUP OFF;

CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO ‘%F’; # default

CONFIGURE DEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO BACKUPSET; # default

CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default CONFIGURE ARCHIVELOG BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default CONFIGURE MAXSETSIZE TO UNLIMITED; # default

CONFIGURE ENCRYPTION FOR DATABASE OFF; CONFIGURE ENCRYPTION ALGORITHM ‘AES128’; CONFIGURE COMPRESSION ALGORITHM ‘zlib’;

CONFIGURE ARCHIVELOG DELETION POLICY TO NONE; # default

CONFIGURE SNAPSHOT CONTROLFILE NAME TO ‘C:\ORACLE\PRODUCT\11.1.0\DB_1\ DATABASE\SNCFORCL.ORA’; # default

3.Configure the retention policy to redundancy of 2:

RMAN> CONFIGURE RETENTION POLICY TO REDUNDANCY 2; old RMAN configuration parameters:

CONFIGURE RETENTION POLICY TO REDUNDANCY 1; new RMAN configuration parameters: CONFIGURE RETENTION POLICY TO REDUNDANCY 2;

new RMAN configuration parameters are successfully stored

4.Configure control-file autobackups on:

RMAN> CONFIGURE CONTROLFILE AUTOBACKUP on; old RMAN configuration parameters: CONFIGURE CONTROLFILE AUTOBACKUP OFF;

new RMAN configuration parameters: