Contents:- Create Backup in Different Ways i.e Backup Set, Image Copy, Archival Backup, Multisection Backup into multipiece backup set, Incremental backup, leve 0 Backup, Level 1 Cumulative Backup, Level 1 Differential Backup

Backup Types

Full Backup                             

Contains all data file blocks.

Level 0 Incremental Backup     

Contains all data file blocks same as full backup but the base for incremental backup.

Level 1 Cumulative Incremental Backup      

Contains only blocks modified since the last level 0 incremental backup.

Level 1 Differential Incremental Backup

Contains only blocks Modified since the last incremental backup(either level 0 or 1).

Creating Backup Sets

Backup set is a collection of one or more files of backup.

RMAN> Backup as backupset format ‘/backup/df_%d_%s_%p.bus’ tablespace scm_data;

Creating Image Copies Backup

Image copy backup means same to same (block to block) backup of a file same as by operating system copy and paste command.

An image copy is a clone of single Datafile, archivelog , redo log or control file.

An image copy can be written only to disk. In Image copy backup time is increased because all blocks are copies whether they contain data or not, but restoration time is reduced. Here oracle database process copies the file and perform additional actions such as Checking for Corrupt blocks and registering the copy in the control file.

RMAN> Configure device type disk backup type to copy;

or

RMAN> Backup as copy Datafile ‘/u01/app/backup/users_01_db01.dbf’;

RMAN> Backup as copy archivelog like ‘/u01/app/backup/arch%’;

To Speedup the process of copying , you can use the NOCHECKSUM Parameter. By default RMAN Computes the checksum of each block backed up, and stores it with the backup. When the backup is restored the checksum(Is mainly used to detect the error) is verified.

An Image copy can be a part of a Full or Incremental Level 0 Backup because a file copy always includes all blocks.

Creating a Whole Database Backup

RMAN> Backup database plus archivelog DELETE INPUT.

9Or

RMAN> run

{

Backup database format device type disk to ‘/u01/app/backup/db_%u_%d_%s’;

Sql ‘alter system archive log current’;

Backup format ‘/u01/app/oracle/backup/archivelog/log_t%t_s%s_%p%p’

(archivelog all delete all input);

}

Fast Recovery Area

Fast Recovery Area would perform space management for you, deleting files when space pressure grows.

Create a Backup (Backup set or image copies) of previous image copies of all files.

RMAN> Backup copy of database;

Incremental Backup

Incremental backup is either level 0 or level 1(cumulative or differential(default)).

RMAN> Alter database enable block change tracking  using file ‘/u01/app/oracle/incremental_backup/record.cts’;

We can rename this block change tracking file but only when the database is in mount stage.

RMAN> backup incremental level 0 database;

RMAN> backup incremental level 1 database;

RMAN> backup incremental level 1 cumulative database;

Monitor Block Change Tracking

SQL> select filename,status,bytes from V$block_Change_Tracking;

SQL> select file#,avg(Datafile_blocks),avg(blocks_read),avg(blocks_read/Datafile_blocks)*100 PCT_READ_FOR_BACKUP, avg(blocks) from V$backup_datafile where used_change_tracking=’YES’ and incremental_level>0 group by file#;

V$backup_datafile view shows how effective the block change tracking is in minimizing the incremental backup I/O (PCT_READ_FOR_BACKUP column). A high value indicates that RMAN reads most blocks in the data file during the incremental backup. You can reduce this ratio by decreasing the time between the incremental backups.

Full Image copy can be incrementally updated

A Full image copy can be incrementally updated by applying incremental backups with the RECOVER Command.

Creating Duplex Backup Set

RMAN> backup as backupset device type sbt copies 2 incremental level 0 database;

Creating Backups of Backup Sets

RMAN> backup device type disk as backupset database plus archivelog;

RMAN> backup device type sbt backupset all;

Skip Read only table space during Backup.

You can specify SKIP READONLY Option of the backup command to let RMAN know do not backup read-only tablespace.

Creating RMAN Multisection Backup.

During the multisection backup a large Datafile is divided into number of section. And each section backup separately into multipiece backupset.

Oracle Datafile can be upto 128 TB in size.

RMAN break up these large files into multiple section and backup and restore these section independently by creating multisection backup.

Multisection backup can only be done with backup sets not with image copies.

Backing up a file into separate sections can improve the performance of the backup operation, and it also allows large files backups to be restarted.

A Multisection backup job produce a multipiece backup sets. Each piece contains one section of the file. All sections of a multisection backup, except for the last section, are of the same size. There are maximum 256 sections per file.

Compatible must be set to at least 11.0

Syntax:

BACKUP <options> SECTION SIZE <integer> [K | M | G]

VALIDATE DATAFILE <options> SECTION SIZE <integer> [ K | M | G ]

Practical

RMAN> backup Datafile 3 section size=25m TAG ‘section25mb’;

Viewing Metadata about multi section backup

V$BACKUP_SET, RC_BACKUP_SET     -

Views have a MULTI_SECTION Column. Which indicates whether this is a multisection backup or not.

V$BACKUP_DATAFILE and RC_BACKUP_DATAFILE

Views have a SECTION_SIZE Column. Which specifies the number of blocks in each section of a multisection backup. Zero means a whole file backup.

Archival Backup

If you need to preserve an online backup for a specified amount of time.  RMAN Automatically assumes that you might want to perform point-In time recovery for any issue since that backup to the present. To Satisfy this RMAN keeps archive log for that time period.

Concepts

Requirements:

Simply keep the specific backup. i.e for two years.  You do not have intention of recovering to a point in time since that backup, but you just want to be able to recover to the exact time of the backup and no later. And parallel you also want to maintain a retention policy that keeps your backup area free of clutter, so making it reach back two years is not acceptable.

Solution

An Archival backup solve this problem. If you mark a backup as an archival backup, that attributes overrides any configured retention policy for the purpose of this backup. This archival backup either considered obsolete only after the time you specified or never.

The KEEP Clause creates an archival backup that is a snapshot of the database at a point in time. The only redo logs that are kept are those required to restore this backup to a consistent state.

Backup created with the KEEP Option include the SPFILE, Control Files and Archived Redo Log Files required to restore this backup and data files.

After the Archival backup is created, it is retained for as long as specified. Even if you have much smaller retention window and run DELETE OBSOLETE command, the archival backup remains.

Archive backup cannot be written to fast recovery area.

Use

The Archival backup can be used to restore the database to another host for testing purpose.

Creating Archival Backups with RMAN

Syntax:

KEEP {FOREVER | UNTIL TIME [=] ‘date_string ‘}

NOKEEP

[ RESTORE POINT rname ]

Practical

Archiving the Database Backup

RMAN> connect target / catalog rman_user/rman_user@catdb

Rman> change backup tag ‘consistent_db_backup’ keep forever; (This is Changes a consistent backup into an archival backup)

Changing the status of a database copy

Rman> change copy of database controlfile NOKEEP; (It will change control file status from keep to nokeep so now it not exempt from the existing retention policy and eligible for obsolete status).

List all Restore Points

RMAN > list restore point all;

Or

RMAN> list restore point ‘restore_point name’;

Backing up Recovery Files.

Backup only the files in the fast recovery area

RMAN> backup recovery area;

Back up all Recovery Files.

RMAN> backup recovery files;

RMAN Backup Related Commands

RMAN>  LIST         Display information about backup sets, copies and image copies recorded in the repository.

RMAN>  REPORT    Produces a detailed analysis of the repository

RMAN> report need backup-  list all data files that requires a backup.

RMAN> report obsolete;  identifies the files that are no longer needed to satisfy backup retention policy.

Report obsolete command reports which  files are obsolete under the currently configured retention policy.

RMAN> crosscheck                   Verifies the status of backup and copies recorded in the RMAN Repository against media such as disk or tape.

RMAN> delete expired     Removes files whose status is expired in rman repository.

RMAN> delete obsolete    Delete backups that are no longer needed.

Dynamic Performance Views Related to Backup.

Target Database

V$backup_set        V$backup_piece    V$datafile_copy     V$backup_files

Recovery Catalog Database

Rc_backup_set       rc_backup_piece    rc_datafile_copy    rc_backup_files

In order to query the RC_BACKUP_FILES view, first execute following command in recovery catalog database.

Sql> call dbms_rcvman.setdatabase(null,null,null,<dbid>);