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>DB_TXN->prepare()</title> 7 <link rel="stylesheet" href="apiReference.css" type="text/css" /> 8 <meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /> 9 <link rel="start" href="index.html" title="Berkeley DB C API Reference" /> 10 <link rel="up" href="txn.html" title="Chapter��12.�� The DB_TXN Handle" /> 11 <link rel="prev" href="txnid.html" title="DB_TXN->id()" /> 12 <link rel="next" href="txnrecover.html" title="DB_ENV->txn_recover()" /> 13 </head> 14 <body> 15 <div class="navheader"> 16 <table width="100%" summary="Navigation header"> 17 <tr> 18 <th colspan="3" align="center">DB_TXN->prepare()</th> 19 </tr> 20 <tr> 21 <td width="20%" align="left"><a accesskey="p" href="txnid.html">Prev</a>��</td> 22 <th width="60%" align="center">Chapter��12.�� 23 The DB_TXN Handle 24 </th> 25 <td width="20%" align="right">��<a accesskey="n" href="txnrecover.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="txnprepare"></a>DB_TXN->prepare()</h2> 35 </div> 36 </div> 37 </div> 38 <pre class="programlisting">#include <db.h> 39 40int 41DB_TXN->prepare(DB_TXN *tid, u_int8_t gid[DB_XIDDATASIZE]); </pre> 42 <p> 43 The <code class="methodname">DB_TXN->prepare()</code> method initiates the beginning of a two-phase 44 commit. 45 </p> 46 <p> 47 In a distributed transaction environment, Berkeley DB can be used as a 48 local transaction manager. In this case, the distributed transaction 49 manager must send <span class="emphasis"><em>prepare</em></span> messages to each local 50 manager. The local manager must then issue a <code class="methodname">DB_TXN->prepare()</code> and 51 await its successful return before responding to the distributed 52 transaction manager. Only after the distributed transaction manager 53 receives successful responses from all of its 54 <span class="emphasis"><em>prepare</em></span> messages should it issue any 55 <span class="emphasis"><em>commit</em></span> messages. 56 </p> 57 <p> 58 In the case of nested transactions, preparing the parent causes all 59 unresolved children of the parent transaction to be committed. Child 60 transactions should never be explicitly prepared. Their fate will be 61 resolved along with their parent's during global recovery. 62 </p> 63 <p> 64 The <code class="methodname">DB_TXN->prepare()</code> <span> 65 <span> 66 method returns a non-zero error value on failure and 0 on success. 67 </span> 68 69 </span> 70 </p> 71 <div class="sect2" lang="en" xml:lang="en"> 72 <div class="titlepage"> 73 <div> 74 <div> 75 <h3 class="title"><a id="id1709775"></a>Parameters</h3> 76 </div> 77 </div> 78 </div> 79 <div class="sect3" lang="en" xml:lang="en"> 80 <div class="titlepage"> 81 <div> 82 <div> 83 <h4 class="title"><a id="id1709784"></a>gid</h4> 84 </div> 85 </div> 86 </div> 87 <p> 88 The <span class="bold"><strong>gid</strong></span> parameter specifies the 89 global transaction ID by which this transaction will be known. This 90 global transaction ID will be returned in calls 91 to <a class="xref" href="txnrecover.html" title="DB_ENV->txn_recover()">DB_ENV->txn_recover()</a> 92 telling the application which global transactions must be resolved. 93 </p> 94 </div> 95 </div> 96 <div class="sect2" lang="en" xml:lang="en"> 97 <div class="titlepage"> 98 <div> 99 <div> 100 <h3 class="title"><a id="id1709682"></a>Class</h3> 101 </div> 102 </div> 103 </div> 104 <p> 105 <a class="link" href="env.html" title="Chapter��5.�� The DB_ENV Handle">DB_ENV</a>, <a class="link" href="txn.html" title="Chapter��12.�� The DB_TXN Handle">DB_TXN</a> 106 </p> 107 </div> 108 <div class="sect2" lang="en" xml:lang="en"> 109 <div class="titlepage"> 110 <div> 111 <div> 112 <h3 class="title"><a id="id1709837"></a>See Also</h3> 113 </div> 114 </div> 115 </div> 116 <p> 117 <a class="xref" href="txn.html#txnlist" title="Transaction Subsystem and Related Methods">Transaction Subsystem and Related Methods</a> 118 </p> 119 </div> 120 </div> 121 <div class="navfooter"> 122 <hr /> 123 <table width="100%" summary="Navigation footer"> 124 <tr> 125 <td width="40%" align="left"><a accesskey="p" href="txnid.html">Prev</a>��</td> 126 <td width="20%" align="center"> 127 <a accesskey="u" href="txn.html">Up</a> 128 </td> 129 <td width="40%" align="right">��<a accesskey="n" href="txnrecover.html">Next</a></td> 130 </tr> 131 <tr> 132 <td width="40%" align="left" valign="top">DB_TXN->id()��</td> 133 <td width="20%" align="center"> 134 <a accesskey="h" href="index.html">Home</a> 135 </td> 136 <td width="40%" align="right" valign="top">��DB_ENV->txn_recover()</td> 137 </tr> 138 </table> 139 </div> 140 </body> 141</html> 142