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 V1.62.4" /> 9 <link rel="home" 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="previous" href="introduction.html" title="Chapter��1.��Introduction" /> 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="introduction.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></div> 36 </div> 37 <p> 38 An important part of DB's transactional guarantees is durability. 39 <span class="emphasis"><em>Durability</em></span> means that once a 40 transaction has been committed, the database modifications performed 41 under its protection will not be lost due to system failure. 42 </p> 43 <p> 44 In order to provide the transactional durability guarantee, 45 DB uses a write-ahead logging system. Every operation performed on 46 your databases is described in a log before it is performed on 47 your databases. This is done in order to ensure that an operation can be 48 recovered in the event of an untimely application 49 or system failure. 50 </p> 51 <p> 52 <span> 53 Beyond logging, another important aspect of durability is 54 recoverability. That is, backup and restore. </span> 55 56 DB supports a normal recovery that runs against a subset of 57 your log files. This is a routine procedure used whenever your 58 environment is first opened upon application startup, and it is intended to 59 ensure that your database is in a consistent state. DB also 60 supports archival backup and recovery in the case of 61 catastrophic failure, such as the loss of a physical disk 62 drive. 63 </p> 64 <p> 65 This book describes several different backup procedures 66 you can use to protect your on-disk data. These procedures 67 range from simple offline backup strategies to hot failovers. Hot failovers 68 provide not only a backup mechanism, but 69 also a way to recover from a fatal hardware failure. 70 </p> 71 <p> 72 This book also describes the recovery procedures you should use 73 for each of the backup strategies that you might employ. 74 </p> 75 <p> 76 For a detailed description of backup and restore procedures, see 77 <span> 78 <a href="filemanagement.html">Managing DB Files</a>. 79 </span> 80 81 82 </p> 83 </div> 84 <div class="navfooter"> 85 <hr /> 86 <table width="100%" summary="Navigation footer"> 87 <tr> 88 <td width="40%" align="left"><a accesskey="p" href="introduction.html">Prev</a>��</td> 89 <td width="20%" align="center"> 90 <a accesskey="u" href="introduction.html">Up</a> 91 </td> 92 <td width="40%" align="right">��<a accesskey="n" href="perftune-intro.html">Next</a></td> 93 </tr> 94 <tr> 95 <td width="40%" align="left" valign="top">Chapter��1.��Introduction��</td> 96 <td width="20%" align="center"> 97 <a accesskey="h" href="index.html">Home</a> 98 </td> 99 <td width="40%" align="right" valign="top">��Performance Tuning</td> 100 </tr> 101 </table> 102 </div> 103 </body> 104</html> 105