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>Multi-threaded and Multi-process Applications</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="apireq.html" title="Application Requirements" /> 12 <link rel="next" href="recovery-intro.html" title="Recoverability" /> 13 </head> 14 <body> 15 <div class="navheader"> 16 <table width="100%" summary="Navigation header"> 17 <tr> 18 <th colspan="3" align="center">Multi-threaded 19 <span>and Multi-process</span> 20 Applications</th> 21 </tr> 22 <tr> 23 <td width="20%" align="left"><a accesskey="p" href="apireq.html">Prev</a> </td> 24 <th width="60%" align="center">Chapter 1. Introduction</th> 25 <td width="20%" align="right"> <a accesskey="n" href="recovery-intro.html">Next</a></td> 26 </tr> 27 </table> 28 <hr /> 29 </div> 30 <div class="sect1" lang="en" xml:lang="en"> 31 <div class="titlepage"> 32 <div> 33 <div> 34 <h2 class="title" style="clear: both"><a id="multithread-intro"></a>Multi-threaded 35 <span>and Multi-process</span> 36 Applications</h2> 37 </div> 38 </div> 39 </div> 40 <p> 41 DB is designed to support multi-threaded <span>and 42 multi-process</span> applications, but their usage means 43 you must pay careful attention to issues of concurrency. 44 Transactions help your application's concurrency by providing various levels of 45 isolation for your threads of control. In addition, DB 46 provides mechanisms that allow you to detect and respond to 47 deadlocks. 48 </p> 49 <p> 50 <span class="emphasis"><em>Isolation</em></span> means that database modifications made by 51 one transaction will not normally be seen by readers from another 52 transaction until the first commits its changes. Different threads 53 use different transaction handles, so 54 this mechanism is normally used to provide isolation between 55 database operations performed by different threads. 56 </p> 57 <p> 58 Note that DB supports different isolation levels. For example, 59 you can configure your application to see uncommitted reads, which means 60 that one transaction can see data that has been modified but not yet 61 committed by another transaction. Doing this might mean your 62 transaction reads data "dirtied" by another transaction, 63 but which subsequently might change before that 64 other transaction commits its changes. 65 On the other hand, lowering your isolation 66 requirements means that your application can experience 67 improved throughput due to reduced lock contention. 68 </p> 69 <p> 70 For more information on concurrency, on managing isolation 71 levels, and on deadlock detection, see <a class="xref" href="txnconcurrency.html" title="Chapter 4. Concurrency">Concurrency</a>. 72 </p> 73 </div> 74 <div class="navfooter"> 75 <hr /> 76 <table width="100%" summary="Navigation footer"> 77 <tr> 78 <td width="40%" align="left"><a accesskey="p" href="apireq.html">Prev</a> </td> 79 <td width="20%" align="center"> 80 <a accesskey="u" href="introduction.html">Up</a> 81 </td> 82 <td width="40%" align="right"> <a accesskey="n" href="recovery-intro.html">Next</a></td> 83 </tr> 84 <tr> 85 <td width="40%" align="left" valign="top">Application Requirements </td> 86 <td width="20%" align="center"> 87 <a accesskey="h" href="index.html">Home</a> 88 </td> 89 <td width="40%" align="right" valign="top"> Recoverability</td> 90 </tr> 91 </table> 92 </div> 93 </body> 94</html> 95