Introduction to RMAN

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Introduction to RMAN
Oracles Backup and Recovery Tool Recovery MANager
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Introduction to RMAN
Oracles Backup and Recovery Tool Recovery MANager
Presented by Paul Hebert/ITEC
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What RMAN does
RMAN creates backups and restores Oracle database
files to tape or disk

• Datafiles
• Controlfiles
• Parameter files
• Archive logs

RMAN will perform consistent and inconsistent
database backups

• Consistent backups must be performed with the
  target database shut down
• Inconsistent (hot) backups require the target
  database is in archivelog mode
• Inconsistent backups require logical recovery
  using archivelogs

RMAN manages information about generated backup
media files

• Backup information is stored in control files
• Backup information optionally stored in an RMAN
  repository catalog
• RMAN can perform point-in-time restoration

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Other RMAN capabilities
RMAN uses disk or tape channels to read and write
to disk or tape media
RMAN tape devices rely on 3rd party Media Manager
software
RMAN permits restartable backups if you have a
specific time window within which backups are
permitted
RMAN can create image copies usable by
user-scripted restore procedures

• Exact copies of target database files

RMAN can create backup sets instead of
traditional image copies
RMAN has a command-line interface (rman) and is
also integrated with Grid Control
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Backup Sets
Backup Sets are logical groupings of backed-up
database files

• Backup sets have a unique ID and may have a TAG
  for RMAN identification
• Backup sets consist of one or more individual
  files called backup pieces.
• Backup piece files contain the data blocks from a
  backup

Backup Sets
RMAN recovery using Backup Sets

• The recovery process identifies the target SCN or
  date to which to recover
• Needed blocks are retrieved from the appropriate
  backup set pieces
• Data files are reconstructed from the needed
  blocks

Backup set media options

• Backup sets can be written to disk or tape
• Backup sets can be compressed by omitting
  unchanged blocks

• Tape backup sets can be encrypted (via Oracle
  Secure Backup)
• Tape backups must use backup sets

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RMAN Backups
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RMAN Channels

• A stream of data to a device using one server
  session
• Server session performs the backup, restore and
  recovery
• Channels can be configured with device-specific
  settings
• Channels are automatically allocated, or manually
  allocated

Channels
RUN ALLOCATE CHANNEL c1 DEVICE TYPE sbt
BACKUP DATABASE PLUS ARCHIVELOG
BACKUP DATAFILE 3 RESTORE TABLESPACE users
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RMAN Media Managers
RMANgt CONFIGURE DEVICE TYPE sbt PARALLELISM 1
RMANgt CONFIGURE DEFAULT DEVICE TYPE TO sbt
RMANgt CONFIGURE CHANNEL DEVICE TYPE sbt PARMS
'ENV(NSR_SERVERbksvr1)' RMANgt BACKUP
DATABASE

• Two types of device type disk and sbt
• RMAN has an open API for communicating with Tape
  and other media manager software
• RMAN sends labeled streams of bytes to the media
  manager during backup
• The labeled streams are returned by the media
  manager during RMAN restore operations

• Media Manager vendors have specific installation
  instructions that vary by vendor
• Refer to vendors for detailed installation and
  use instructions

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RMAN backup output media
Backup Set

• RMAN-proprietary storage of backed-up data blocks
• Consist of a Backup Set identifier plus
  associated backup set files or pieces
• Can only be restored using RMAN

Image Copy

• Equivalent to file copies of original database
  files
• RMAN considers user-managed backups as Image
  Copies
• Contain ALL data blocks no compression

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RMAN Tags
Backup sets or image copies can be labeled with a
text TAG
RMAN commands can select backup sets or copies
using the TAG
TAGs are visible in RMAN list or report output
BACKUP AS COPY DATABASE TAGfull_cold_copy
BACKUP AS COPY COPY OF DATABASE FROM
TAGfull_cold_copy TAGnew_full_cold_copy
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RMAN backup types
Full backup

• Backup of all specified database file blocks
• Independent of when database files were last
  backed up
• Not used in incremental backup strategies

Incremental backup

• Backup of blocks changed since last incremental
  backup
• SCN used to identify changed blocks
• Level 0 incremental backup
• Level 1 incremental backup

Full backup is equivalent to incremental level 0
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Incremental Backup Types
Level 0 incremental backups

• Backup of all blocks in specified database files
• Independent of when files were last backed up
• Base for subsequent Level 1 backups

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Incremental Backup Types
Level 1 incremental backups
Differential backup Contain all blocks changed
after the most recent incremental backup at level
1 or 0

• Differential backups remain smaller and quicker
  to perform
• Differential backups are slower to restore
  requiring changes in multiple earlier incremental
  backups

Cumulative backup Contain all blocks changed
after the most recent incremental backup at level
0

• Cumulative backups become much larger over time
• Cumulative backups are quicker to restore

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Other RMAN capabilities
RMAN can report, validate, remove or protect
backup files
RMAN performance controls

• RMAN can throttle disk I/O rate during backup and
  restore
• RMAN can limit the number and size of backup set
  files

RMAN can use a Block Change Tracking file to
identify changed blocks

• Bitmap file created automatically by Level 0
  backup if configured
• RMAN can now avoid rescanning database files for
  changed blocks
• (blocks with newer SCN than in previous backup
  sets)
• Loss of change tracking file is harmless
  recreated by next Level 0

Change Tracking file can introduce database
overhead you need to evaluate if it is worth the
extra performance hit
RMAN and missing Level 0 backups

• RMAN will create a missing Level 0 backup
  automatically when asked to perform a Level 1
  backup

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Other RMAN capabilities
RMAN actions can be scripted and scheduled using
cron or dbms_job
RMAN can backup and restore your Flash Recovery
Area
RMAN can clone (duplicate) databases using the
AUXILIARY connection
RMAN can use and manage ASM files
RMAN can switch an instance to use a copy of a
database or datafiles
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What doesnt RMAN do?
RMAN does not automatically enforce your
retention policies
RMAN does not automatically delete expired backup
files
RMAN does not automatically detect missing backup
files
RMAN does not backup any other types of files

• Oracle code tree
• Other operating system files
• Alert logs and traces
• Oracle Wallet files

RMAN is not upward or downward version compatible

• You must backup 10g databases with 10g RMAN!
• You can only backup 9i databases with 9i RMAN!
• 10g and 9i cant share a repository!

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Cumulative Incremental Backup Strategy
Increasing backup set size and backup
duration Faster recovery
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Differential Incremental Backup Strategy
Consistent backup set size and backup
duration Slower recovery using more backup sets
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Mixed Incremental Strategy

1. Monthly Full Level 0 Incremental backup

1. Weekly Level 1 Cumulative Incremental backup

1. Daily Level 1 Differential Incremental backup

• Advantages
• RMAN doesnt have to apply more than a few days
  worth of differential backups to the latest
  cumulative backup and the original level 0 backup
• No more than 1 day of redo logs need to be
  applied during recovery
• Disadvantages
• May not meet with your MTTR target
  (Mean-Time-to-Recovery)

Rule of Thumb You should perform a new Level 0
backup once gt50 of blocks have changed
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Channel Parallelism in RMAN
Allocating multiple channels for a device type
allows parallel completion of RMAN tasks
Manual channel allocation has to happen inside a
RUN block
Device types can be configured for automatic
allocation of parallel channels
CONFIGURE DEVICE TYPE DISK PARALLELISM 2
Multiple channels can be used to write to
multiple devices simultaneously
If a channel fails, surviving channels will
attempt to complete the restore job
RUNALLOCATE CHANNEL c1 DEVICE TYPE
sbtALLOCATE CHANNEL c2 DEVICE TYPE
sbtALLOCATE CHANNEL c3 DEVICE TYPE sbtBACKUP
DATAFILE 5,6,7
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RMAN Restore and Recovery
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Database Recovery Procedure
Two Steps
RESTORE

• Missing files are restored from the blocks in
  backup sets OR
• Image copies are copied to the original (or new)
  file locations
• Unmodified files not modified can be skipped by
  RMAN automatically

• RMAN uses the record of available backups in the
  RMAN repository to select the best available
  backups for use in the restore operation.
• The most recent backup available, or the most
  recent backup satisfying any UNTIL clause
  specified in the RESTORE command, is always the
  preferred choice
• If two backups are from the same point in time,
  RMAN prefers image copies over backup sets
  because RMAN image copy restores are faster

RECOVER

• Recovery must be performed for incomplete backups
• Archive logs are applied to the database

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Reusing RMAN Procedures
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RMAN scripting

• Reusable lists of RMAN commands

• Stored on the file system or in the RMAN
  respository
• Not the Control file!

script

• LOCAL scripts used by a single database instance

• GLOBAL scripts shared by database instances in
  repository

create recovery catalog script to back up
database and archived logs CREATE SCRIPT
backup_whole COMMENT "backup whole database and
logs" BACKUP INCREMENTAL LEVEL 0 TAG
b_whole_l0 DATABASE PLUS ARCHIVELOG
creates recovery catalog script to back up
database and archived logs CREATE GLOBAL SCRIPT
global_backup_db COMMENT "backup any database
from the recovery catalog, with logs"
BACKUP DATABASE PLUS ARCHIVELOG
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Useful RMAN commands
Execute a command on the local host from within
RMAN
host
host dd if/orabak/tools.dbf of/oradata/tools.db
f
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Useful RMAN commands
Execute a SQL command on the Target database
within RMAN
sql
sql alter system archive log current
Select statements not supported
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Managing RMAN backups
list / report crosscheck validate delete
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Managing RMAN backups
List all backup sets and pieces known by RMAN
list / report
May not represent actual files available on disk
LIST BACKUP OF DATABASE ARCHIVELOG ALL lists
known backups of db files and logsLIST COPY
lists only image copiesLIST BACKUP
lists all RMAN backup media REPORT NEED
BACKUP report which database files need backup
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Managing RMAN backups
Verifies existence of known backup file sets and
pieces in the RMAN repository
Marks backup file sets and pieces as expired if
they exceed retention policies
crosscheck
CROSSCHECK doesnt physically delete anything!
CROSSCHECK BACKUPSET crosschecks backup sets
on disk and SBT CROSSCHECK BACKUP crosscheck
all RMAN backup media
RMAN backup files have four possible states in
the repository
AVAILABLE
UNAVAILABLE
EXPIRED
OBSOLETE
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Managing RMAN backups
Verifies existence and availability of database
file media
Checks for corrupted blocks and reports them in
VDATABASE_BLOCK_CORRUPTION
validate
Damaged backup file media may be repaired using
Block Media Recovery
BACKUP VALIDATE DATABASE ARCHIVELOG ALL RESTORE
CONTROLFILE VALIDATE RESTORE ARCHIVELOG ALL
VALIDATE RESTORE DATAFILE 4,5,6 VALIDATE
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Managing RMAN backups
Remove any or all database backup file media from
disk/tape and RMAN repository
Can remove obsolete media no longer needed to
recover under retention policies
delete
DELETE BACKUP TAG'before_upgrade' delete
backup based on tag DELETE NOPROMPT ARCHIVELOG
ALL delete all archivelogs DELETE EXPIRED
BACKUP delete expired after
crosscheck DELETE BACKUP delete ALL backups
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RMAN Web Management in Grid Control
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Jump in and use RMAN!
It is easier to show RMAN (and not just talk
about it endlessly )
rman target system/pswd_at_sid1
rman rmangtgt connect target system/pswd_at_sid1
rman target system/pswd_at_sid1 catalog
rman/pswd_at_rmansid
rman target system/pswd_at_sid1 catalog
rman/pswd_at_rmansid auxiliary system/pswd_at_sid2
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backup database
Simple database backup

• Uses default device type setting (SBT or Disk)
• Creates device channels according to parallelism
  setting
• Creates image copies or backup sets
• Might not backup controlfile automatically!
• Doesnt backup archivelogs

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Inconsistent database backup including archive
logs
Inconsistent database backup
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show controlfile autobackupconfigure controlfile
autobackup on
How do I ensure the controlfile is always backed
up?
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show parameterALLconfigure parameter
clearconfigure parameter newsetting
Setting and clearing Configuration Parameters
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Restore and Recover
restore and recover
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RMAN 11g Features
RMAN 11g Features

• Parallel backup of regions of BIG datafiles
• New encryption algorithm
• Data Recovery Advisor 11g
• Online backup of standby databases
• Virtual, secure and mergeable RMAN catalogs
• Encrypted disk backup sets

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Thanks for your attention!
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References

• Oracle Database Backup and Recovery Basics10g
  Release 2 (10.2) http//download.oracle.com/docs/c
  d/B19306_01/backup.102/b14192/bkup004.htmsthref38
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• Oracle Database Backup and Recovery Advanced
  User's Guide 10g Release 2 (10.2)
• http//download-east.oracle.com/docs/cd/B14117_01/
  server.101/b10734/toc.htm
• Oracle Database Backup and Recovery
  Reference10g Release 2 (10.2)
• http//download-west.oracle.com/docs/cd/B19306_01/
  backup.102/b14194/toc.htm
• Freeman Hart, Oracle9i RMAN Backup Recovery,
  Oracle Press
• (useful 3rd party media manager chapters)
• http//www.mhprofessional.com/product.php?cat7is
  bn0072226625