Book Image

PostgreSQL 9 Admin Cookbook

By : Simon Riggs, Hannu Krosing
Book Image

PostgreSQL 9 Admin Cookbook

By: Simon Riggs, Hannu Krosing

Overview of this book

<p>PostgreSQL is a powerful, open source object-relational database system. An enterprise database, PostgreSQL includes features such as Multi-Version Concurrency Control (MVCC), point-in-time recovery, tablespaces, asynchronous replication, nested transactions (savepoints), online/hot backups, a sophisticated query planner/optimizer, and write-ahead logging for fault tolerance. PostgreSQL 9 Admin cookbook covers everything a database administrator needs to protect, manage and run a healthy and efficient PostgreSQL 9.0 database.</p> <p>PostgreSQL 9 Admin Cookbook describes key aspects of the PostgreSQL open source database system. The book covers everything a sysadmin or DBA needs to protect, manage, and run a healthy and efficient PostgreSQL 9 database. This hands-on guide will assist developers working on live databases, supporting web or enterprise software applications using Java, Python, Ruby, or .Net from any development framework. It's easy to manage your database when you've got PostgreSQL 9 Admin Cookbook to hand.</p> <p>PostgreSQL is fast becoming one of the world's most popular server databases with an enviable reputation for performance, stability, and an enormous range of advanced features. PostgreSQL is one of the oldest open source projects, completely free to use and developed by a very diverse worldwide community. Most of all, It Just Works!</p> <p>PostgreSQL 9 Admin Cookbook offers the information you need to manage your live production databases on PostgreSQL. The book contains insights direct from the main author of the PostgreSQL replication and recovery features, and the database architect of the most successful startup using PostgreSQL, Skype.</p> <p>This practical guide gives quick answers to common questions and problems, building on the authors' experience as trainers, users, and core developers of the PostgreSQL database server.</p> <p>Each technical aspect is broken down into short recipes that demonstrate solutions with working code then explain why and how that works. The book is intended to be a desk reference for both new users and technical experts.</p> <p>The book covers all the latest features in PostgreSQL 9. Soon you will be running a smooth database with ease!</p>
Table of Contents (18 chapters)
PostgreSQL 9 Administration Cookbook
Credits
About the Authors
About the Reviewers
Preface
Index

Understanding and controlling crash recovery


Crash recovery is the PostgreSQL subsystem that saves us if the server should crash, or fail as a part of a system crash.

It's good to understand a little about it, and to do what we can to control it in our favor.

How to do it...

If PostgreSQL crashes there will be a message in the server log with severity-level PANIC. PostgreSQL will immediately restart and attempt to recover using the transaction log or Write Ahead Log (WAL).

The WAL consists of a series of files written to the pg_xlog subdirectory of the PostgreSQL data directory. Each change made to the database is recorded first in WAL, hence the name "write-ahead" log. When a transaction commits, the default and safe behavior is to force the WAL records to disk. If PostgreSQL should crash, the WAL will be replayed, which returns the database to the point of the last committed transaction, and thus ensures the durability of any database changes.

Note that the database changes themselves aren...