With any database system, backup is one of the most important tool. PostgreSQL, The most Advanced Open Source database facilitates various backup and recovery options: * Logical Backup * Physical Backup * Archive Logging * Point in Time Recovery

1. Backup-Recovery in PostgreSQL
Logical Backup, Physical Backup and PITR
15/7/2013

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© 2012 EnterpriseDB. All rights reserved.
Available Backup and Recovery Tools
Physical and Logical Backup
Logical Backup using pg_dump
Instance level logical backup using pg_dumpall
Table level, Schema level or DB level logical backup
Different file formats available for pg_dump backup
pg_restore to restore binary backup with pg_dump
Physical Backups
• pg_basebackup
• Compressed backup
• Recovery with WAL and archived WAL
• Recover to the point of crash
• Point in Time Recover to recover from data corruption due to a bad query/batch
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Online Backup
 Enable Archiving
• archive_command = 'cp %p /mnt/server/archivedir/%f‘
• wal_level = archive
• Archive_mode = on
 Take a backup
• SELECT pg_start_backup('label');
• Take a backup (file system level copy)
• SELECT pg_stop_backup();
 Alternative to Manual backup: Use pg_basebackup for taking a backup
• pg_basebackup -D /opt/PostgresPlus/9.2AS/data -h 192.168.160.147 -W -p 5444 -Fp --xlog-
method=stream
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Recovery: Restore the server
 Stop the server, if it's running. Change the
pg_hba.conf to disallow user’s login during recovery
 Keep a backup of original server or at least pg_xlog
 Restore the database files from your file system
backup. Be sure about the ownership and soft links
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Recovery: Prepare the Server
 Remove any files present in pg_xlog/;
 If you have unarchived WAL segment files that you saved (step 2), copy them into
pg_xlog/
 Create a recovery command file recovery.conf in the cluster data directory:
• restore_command = 'cp /mnt/server/archivedir/%f "%p" '
 If this is a point in time recovery to recover from a bad batch operation or a bad
command which has corrupted the data then add recovery_target_time to a timestamp
which is just before the bad command/batch was fired
• recovery_target_time = '18-JUL-13 23:07:05.39855'
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Start the Recovery
 Start the server
• The server will go into recovery mode and proceed to read through the archived
WAL files it needs
• Should the recovery be terminated because of an external error, the server can
simply be restarted and it will continue recovery
• Upon completion of the recovery process, the server will rename recovery.conf to
recovery.done
 Inspect the contents of the database to ensure you have
recovered to the desired state. If not, restart the whole
process
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7. Sameer Kumar
Ashnik Pte Ltd, Singapore
www.ashnik.com | sameer.kumar@ashnik.com
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