Backup & Recovery with RMAN


Agenda


• Types of failures and backups in Oracle
• RMAN Architecture
• Manual vs. RMAN backups
• On-tape backups with RMAN
• RMAN Configuration
• RMAN backup strategies
• RMAN backups Syntax
• Exemplary recovery scanarios



Types of failures

• Instance Failure
– Usually connected with an Oracle process failure
• Media Failure
– Disk failure, storage array controller failure etc.
• Human error
– In most cases accidentally deleted/updated data
– Database user or DBA
• Disaster
– Fire, flood, earthquake, plane crash etc.

Backup options in Oracle

• Physical backups
– Cold (off-line) backups
• Full database only
• Require downtime
– Hot (on-line) backups
• Different types of backups: full, incr. (cumulative, differential), archivelogs
• cumulative backup: which backs up all blocks changed after the most recent incremental backup at level 0
• differential backup: which backs up all blocks changed after the most recent incremental backup at level 1 or 0
• Different scopes: full database, tablespace(s) or datafile(s)
• Do not require database downtime
• Can be used to recover full database, single/multiple tablespace(s)/datafile(s) or a corrupted block
• Database can be recovered to any point in time within assumed backup retention period

RMAN architecture
Types of RMAN hot backups


• Copy or backupset
• Full database backup
• Incremental backups (in 10g 2 levels available: 0 and 1)
– Cumulative, differential
• Archivelog backups
• Tablespace(s), datafile(s) backups


Manual vs. RMAN backups

• RMAN advantages:
– Supports incremental backup strategies
– RMAN on-line backups are not so heavy for the system as manual on-line backups
– RMAN can detect corrupted blocks
– RMAN automatically track database structure changes
– Provides easy, automated backup, restore and recovery operations
– Keeps invenotory of taken backups
– Can seamlessly work with third party media managers

• Disadvantage: something new to learn
– RMAN concepts and command syntax sometimes are not intuitive

On-tape backups with RMAN
• RMAN allows to take on-disk backups out of the box
– Flash recovery area, if configured, further simplifies such backups
– On disk backups are interesting but usually not sufficient for a disaster recovery
• On-disk backups can be manually sent to tapes
– Recovery can be very troublesome
• RMAN can seamlessly work with third party Media Managers
– Media Manager Library (MML) is required
– Different configuration tasks for different MMLs
• Many vendors of Media Management software provide MMLs
• Most popular are:
– Tivoli Storage Manager
– Veritas NetBackup

RMAN Configuration


• RMAN can be preconfigured
– Configuration is stored in the control file and in the recovery catalog (if used)
– Can facilitate backup automation
• Most useful settings:

RMAN Configuration

• Example:

configure RETENTION POLICY TO RECOVERY WINDOW OF 31 DAYS;
configure DEFAULT DEVICE TYPE TO 'sbt';
configure DEVICE TYPE 'sbt' PARALLELISM 2;
configure CHANNEL DEVICE TYPE ‘sbt’ parms='ENV=
(TDPO_OPTFILE=/opt/tivoli/tsm/client/oracle/bin/tdpo.opt)';
configure DEVICE TYPE DISK PARALLELISM 2;
configure MAXSETSIZE TO 200 G;
configure archivelog backup copies for device type 'sbt' to 1;
configure controlfile autobackup on;

• The SHOW ALL command lists all RMAN configuration settings
• To clear a given settings append CLEAR at the end of the CONFIGURE command


RMAN backup strategies


• RMAN allows many types of backups
• It possible to build own backup strategy that suits given database best
• Both Oracle-recommended strategies implemented for all production systems
• Incremental backup strategy:
– Backups go to tapes
– Weekly or biweekly level 0 backups (depending on the DB size)
– A level 1 cumulative backup inbetween
– Daily incremental level 1 differential backups
– Archivelog backup every 30 minutes
• Incrementally updated DB copy strategy:
– daily incremental differential backups applied with 2 days of delay
– Copies, incremental backups and archived redo logs stored in the Flash Recovery Area

Backup operations

RMAN> RUN {
ALLOCATE CHANNEL disk1 DEVICE TYPE DISK/SBT
FORMAT '/u01/backups/%U';
BACKUP DATABASE PLUS ARCHIVELOG;
}
Backup operations
Backup operations


RMAN> backup as copy database;
RMAN> backup copy of database;
RMAN> backup database;



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

RMAN> backup as compressed backupset full database plus archivelog;


Complete database recovery

• Needed when:
– All datafiles are lost or the SYSTEM tablespace datafiles are lost
– At least one member of each redo log group survived
• Requires:
– Control file recovery (if it’s lost)
– Datafile restore from a backup
– Database recovery using incremental backups and/or archived redo logs and online redo logs
Database point-in-time recovery

• Needed when:
– all datafiles are lost
– All copies of the current control file are lost
– Or all online redo log group members are lost
• If done after a disaster it has to be preceded by:
– Hardware configuration
– OS and Oracle software installation
– Re-creation or restore from non-RMAN backup of listener.ora, tnsnames.ora and other important configuration files
– ASM instance and diskgroup configuration (if needed)
– MML installation and configuration
• Requires
– Spfile restore
– Controlfile restore
– Datafiles restore and recovery

Recovery
Tablespace point-in-time recovery
• Needed
– Mainly to address a human error
• Oracle makes efforts to automate it
– Can be done with few clicks in OEM
• Requires
– Point in time recovery of the whole database Export/import of selected tablespaces schemas or objects


Block media recovery

• Needed when:
– Database reports either single or multi block corruption
• Can be done with an open database
• Database corruptions can be discovered with RMAN backup validate database command
• Corrupted blocks can be found in V$DATABASE_BLOCK_CORRUPTION

Single/multiple datafile/tablespace recovery

• Needed when
– Single/multiple tablespaces or datafiles have been lost
– SYSTEM tablespace is intact
– Controlfiles and online redo logs are intact
• Requires
– To put offline datafiles and tablespaces being recovered
– The database can be open and available to users

v$views
• V$BACKUP_ARCHIVELOG_DETAILS
• V$BACKUP_ARCHIVELOG_SUMMARY
• V$BACKUP_CONTROLFILE_DETAILS
• V$BACKUP_CONTROLFILE_SUMMARY
• V$BACKUP_COPY_DETAILS
• V$BACKUP_COPY_SUMMARY
• V$BACKUP_PIECE_DETAILS
• V$RMAN_BACKUP_JOB_DETAILS
• V$RMAN_BACKUP_TYPE
• V$FLASH_RECOVERY_AREA_USAGE

v$views
DBA_HIST_INSTANCE_RECOVERY
DBA_RECOVERABLE_SCRIPT
DBA_RECOVERABLE_SCRIPT_BLOCKS
DBA_RECOVERABLE_SCRIPT_ERRORS
DBA_RECOVERABLE_SCRIPT_PARAMS
GV_$INSTANCE_RECOVERY
GV_$RECOVER_FILE
GV_$RECOVERY_FILE_STATUS
GV_$RECOVERY_LOG
GV_$RECOVERY_PROGRESS
GV_$RECOVERY_STATUS
V_$FLASH_RECOVERY_AREA_USAGE
V_$INSTANCE_RECOVERY
V_$RECOVER_FILE
V_$RECOVERY_FILE_DEST
V_$RECOVERY_FILE_STATUS
V_$RECOVERY_LOG
V_$RECOVERY_PROGRESS
V_$RECOVERY_STATUS

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