There are multiple reasons to restore a database from a backup. Under rare circumstances, this might even become necessary in a production environment. In that case, the business will probably require you to restore to the latest point in time, known to hold valid data. This presentation examines specific scenarios to achieve minimal or no data loss using point-in-time recovery (PITR) to an exact date and time, a particular transaction, and a savepoint. Target Audience: This presentation is intended for solution architects and DBAs, who are responsible for designing and supporting Postgres database environments.

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How to get your data back in Postgres – Point-in-Time
Recovery (PITR) explained
For more information on Postgres PITR please email sales@enterprisedb.com or visit www.enterprisedb.com

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Agenda
• Introduction
• Business Impact vs Cost
• Downtime Scenarios
• Backup Methods
• Point-In-Time Recovery
• Summary

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• Disaster recovery strategies are key to the reliable operation of any
business-critical environment.
• Backup and recovery plans must consider various failure scenarios and
compliance requirements, including device failure, operator error, and data
corruption.
Introduction

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Business Impact vs Cost
• How long will recovery take?
• How long do we need to store backup data?
• How much will data storage cost?
• Will an outage effect our brand?
• Can any part of the database remain operational whilst
I recover elsewhere?
• Do I know when the problem I am recovering from
started?

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Downtime Scenarios

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• As with any database, a Postgres database should be backed up regularly.
• There are three fundamentally different approaches to backing up
Postgres data:
− SQL dump
− File system level backup
− Continuous archiving
Backup Methods

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• Generate a text file with SQL commands
• Postgres provides the utility program pg_dump for this purpose.
• pg_dump does not block readers nor writers.
• Dumps created by pg_dump are internally consistent, that is, the dump
represents a snapshot of the database as of the time pg_dump begins
running.
• Syntax:
pg_dump [options] [dbname]
Backup – SQL Dump

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Backup – Entire Cluster – SQL Dump
• pg_dumpall is used to dump an entire database cluster in plain-text SQL
format
• pg_dumpall dumps global objects: users, groups, and associated
permissions
• Use PSQL to restore
• Syntax:
pg_dumpall [options] > filename.backup

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• Copy Postgres files from the file system.
• You can use whatever method you prefer for doing usual file system
backups, for example:
tar -cvf backup.tar /usr/local/pgsql/data
• The database server must be shut down in order to get a usable backup.
• File system backups only work for complete backups and recovery of an
entire database cluster.
Backup – Cold Backup

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• Database can stay operational during backup.
• Postgres maintains WAL logs for all transactions in the pg_xlog directory.
• When full, Postgres automatically switches WAL logs.
• Continuous archiving can be setup to keep a copy of switched WAL logs
which can later be used for recovery.
• Enables online file system backup of a database cluster.
• Requirements:
wal_level = archive
archive_mode = on
archive_command = …
Backup – Hot Backup

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1. Connect using psql and issue SELECT pg_start_backup(‘any
useful label’);
2. Use a standard file system backup utility to back up the data directory.
3. Connect using psql and issue SELECT pg_stop_backup();
4. Ensure to continuously archive WAL logs.
Online Base Backup

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• pg_basebackup takes a base backup of a Postgres cluster.
• Backup can be used to setup a standby with streaming replication and a
Point-In-Time Recovery (PITR).
• pg_basebackup takes a binary copy of the database cluster files.
• pg_basebackup puts the database in and out of backup mode.
Online Base Backup using pg_basebackup

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• Point-in-time recovery (PITR) is the ability to restore a database cluster up
to the present or to a specified point of time in the past.
• Uses a full database cluster backup and applies the WAL logs.
• Must be configured before it is needed. WAL log archiving must be
enabled.
• Must have information of when you want to recover to.
Point-in-Time Recovery

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Point-in-Time Recovery Demo

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• pause_at_recovery_target = true
• hot_standby = on (if using pause_at_recovery_target)
• SELECT pg_is_xlog_replay_paused();
• SELECT pg_xlog_replay_resume();
• SELECT pg_catalog.pg_current_xlog_location();
• SELECT pg_xlogfile_name(’output from above command');
• SELECT pg_create_restore_point('webinar_restore');
Point-In-Time Recovery Help

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Summary
• Introduction
• Business Impact vs Cost
• Backup and Recovery Methods
− SQL Dump
− Cold Backup (offline Backup)
− Hot Backup (online Backup)
− Continuous Archiving
• Point-In Time Recovery
• Demo

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• EDB Postgres Advanced Server 9.5 Download
http://www.enterprisedb.com/downloads/postgres-postgresql-downloads
• Continuous Archiving and Point-in-Time Recovery (PITR)
http://www.postgresql.org/docs/current/static/continuous-archiving.html
• pg_dump
http://www.postgresql.org/docs/9.5/static/app-pgdump.html
• pg_dumpall
http://www.postgresql.org/docs/current/static/app-pg-dumpall.html
• pg_basebackup
http://www.postgresql.org/docs/current/static/app-pgbasebackup.html
Contact sales@enterprisedb.com for more information on Postgres PITR
Resources

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• Take advantage of the most convenient training that best fits your learning style and get
Postgres certified!
− EDB offers Classroom & on-site training globally
− Live virtual training courses can be taken from any location and maintains live communication
with the instructor to guide you and answer questions quickly.
• EDB’s eSubscriptions
− This annual subscription provides access to the entire EDB library of on-demand training
courses for convenient access and training any time.
• Postgres Training Credits (PTC)
− Training credits provide the flexibility to pre-purchase blocks of training credits that can be spent
on any combination of our training delivery methods. It is a convenient way to receive training
with a built-in price discount.
• Earn an Associate-level or Professional-level Postgres Certification
To learn more about EDB’s training schedule, Certification, eSubscriptions and Training Credits email
training@enterprisedb.com
Sharpen your skills with Training and Certification

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