1<?xml version="1.0" encoding="UTF-8" standalone="no"?> 2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 3<html xmlns="http://www.w3.org/1999/xhtml"> 4 <head> 5 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> 6 <title>Recoverability</title> 7 <link rel="stylesheet" href="gettingStarted.css" type="text/css" /> 8 <meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /> 9 <link rel="start" href="index.html" title="Getting Started with Berkeley DB Transaction Processing" /> 10 <link rel="up" href="introduction.html" title="Chapter 1. Introduction" /> 11 <link rel="prev" href="multithread-intro.html" title="Multi-threaded and Multi-process Applications" /> 12 <link rel="next" href="perftune-intro.html" title="Performance Tuning" /> 13 </head> 14 <body> 15 <div class="navheader"> 16 <table width="100%" summary="Navigation header"> 17 <tr> 18 <th colspan="3" align="center">Recoverability</th> 19 </tr> 20 <tr> 21 <td width="20%" align="left"><a accesskey="p" href="multithread-intro.html">Prev</a> </td> 22 <th width="60%" align="center">Chapter 1. Introduction</th> 23 <td width="20%" align="right"> <a accesskey="n" href="perftune-intro.html">Next</a></td> 24 </tr> 25 </table> 26 <hr /> 27 </div> 28 <div class="sect1" lang="en" xml:lang="en"> 29 <div class="titlepage"> 30 <div> 31 <div> 32 <h2 class="title" style="clear: both"><a id="recovery-intro"></a>Recoverability</h2> 33 </div> 34 </div> 35 </div> 36 <p> 37 An important part of DB's transactional guarantees is durability. 38 <span class="emphasis"><em>Durability</em></span> means that once a 39 transaction has been committed, the database modifications performed 40 under its protection will not be lost due to system failure. 41 </p> 42 <p> 43 In order to provide the transactional durability guarantee, 44 DB uses a write-ahead logging system. Every operation performed on 45 your databases is described in a log before it is performed on 46 your databases. This is done in order to ensure that an operation can be 47 recovered in the event of an untimely application 48 or system failure. 49 </p> 50 <p> 51 <span> 52 Beyond logging, another important aspect of durability is 53 recoverability. That is, backup and restore. </span> 54 55 DB supports a normal recovery that runs against a subset of 56 your log files. This is a routine procedure used whenever your 57 environment is first opened upon application startup, and it is intended to 58 ensure that your database is in a consistent state. DB also 59 supports archival backup and recovery in the case of 60 catastrophic failure, such as the loss of a physical disk 61 drive. 62 </p> 63 <p> 64 This book describes several different backup procedures 65 you can use to protect your on-disk data. These procedures 66 range from simple offline backup strategies to hot failovers. Hot failovers 67 provide not only a backup mechanism, but 68 also a way to recover from a fatal hardware failure. 69 </p> 70 <p> 71 This book also describes the recovery procedures you should use 72 for each of the backup strategies that you might employ. 73 </p> 74 <p> 75 For a detailed description of backup and restore procedures, see 76 <span> 77 <a class="xref" href="filemanagement.html" title="Chapter 5. Managing DB Files">Managing DB Files</a>. 78 </span> 79 80 81 </p> 82 </div> 83 <div class="navfooter"> 84 <hr /> 85 <table width="100%" summary="Navigation footer"> 86 <tr> 87 <td width="40%" align="left"><a accesskey="p" href="multithread-intro.html">Prev</a> </td> 88 <td width="20%" align="center"> 89 <a accesskey="u" href="introduction.html">Up</a> 90 </td> 91 <td width="40%" align="right"> <a accesskey="n" href="perftune-intro.html">Next</a></td> 92 </tr> 93 <tr> 94 <td width="40%" align="left" valign="top">Multi-threaded 95 <span>and Multi-process</span> 96 Applications </td> 97 <td width="20%" align="center"> 98 <a accesskey="h" href="index.html">Home</a> 99 </td> 100 <td width="40%" align="right" valign="top"> Performance Tuning</td> 101 </tr> 102 </table> 103 </div> 104 </body> 105</html> 106