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>env txn</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 TCL API Reference" /> 10 <link rel="up" href="tclapi.html" title="Chapter��1.�� Berkeley DB Tcl APIs" /> 11 <link rel="prev" href="env_remove.html" title="berkdb envremove" /> 12 <link rel="next" href="txn_abort.html" title="txn abort" /> 13 </head> 14 <body> 15 <div class="navheader"> 16 <table width="100%" summary="Navigation header"> 17 <tr> 18 <th colspan="3" align="center"><span class="emphasis"><em>env</em></span> txn</th> 19 </tr> 20 <tr> 21 <td width="20%" align="left"><a accesskey="p" href="env_remove.html">Prev</a>��</td> 22 <th width="60%" align="center">Chapter��1.�� 23 Berkeley DB Tcl APIs 24 </th> 25 <td width="20%" align="right">��<a accesskey="n" href="txn_abort.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="txn"></a><span class="emphasis"><em>env</em></span> txn</h2> 35 </div> 36 </div> 37 </div> 38 <pre class="programlisting">env txn 39 [-nosync] 40 [-nowait] 41 [-parent txnid] 42 [-sync] </pre> 43 <p> 44 The <span class="emphasis"><em>env</em></span> <span class="bold"><strong>txn</strong></span> 45 command begins a transaction. The returned transaction handle is 46 bound to a Tcl command of the form <span class="bold"><strong>env.txnX</strong></span>, where X is an integer starting at 0 47 (for example, env0.txn0 and env0.txn1). It is through this Tcl command 48 that the script accesses the transaction methods. 49 </p> 50 <p> 51 The options are as follows: 52 </p> 53 <div class="itemizedlist"> 54 <ul type="disc"> 55 <li> 56 <p> 57 <span class="bold"><strong>-nosync</strong></span> 58 </p> 59 <p> 60 Do not synchronously flush the log when this transaction commits or 61 prepares. This means the transaction will exhibit the ACI (atomicity, 62 consistency, and isolation) properties, but not D (durability); that 63 is, database integrity will be maintained, but it is possible that 64 this transaction may be undone during recovery instead of being 65 redone. 66 </p> 67 <p> 68 This behavior may be set for an entire Berkeley DB environment as part 69 of the <span class="bold"><strong>berkdb env</strong></span> call. 70 </p> 71 </li> 72 <li> 73 <p> 74 <span class="bold"><strong>-nowait</strong></span> 75 </p> 76 <p> 77 If a lock is unavailable for any Berkeley DB operation performed in 78 the context of this transaction, throw a Tcl error immediately instead 79 of blocking on the lock. 80 </p> 81 </li> 82 <li> 83 <p> 84 <span class="bold"><strong>-parent txnid</strong></span> 85 </p> 86 <p> 87 Create the new transaction as a nested transaction, with the specified 88 transaction indicated as its parent. Transactions may be nested to 89 any level. 90 </p> 91 </li> 92 <li> 93 <p> 94 <span class="bold"><strong>-sync</strong></span> 95 </p> 96 <p> 97 Synchronously flush the log when this transaction commits or prepares. 98 This means the transaction will exhibit all of the ACID (atomicity, 99 consistency, isolation, and durability) properties. 100 </p> 101 <p> 102 This behavior is the default for Berkeley DB environments unless the 103 <span class="bold"><strong>-nosync</strong></span> option was specified to the 104 <span class="bold"><strong>berkdb env</strong></span> call. 105 </p> 106 </li> 107 </ul> 108 </div> 109 <p> 110 The <span class="emphasis"><em>env</em></span> <span class="bold"><strong>txn</strong></span> 111 command returns a transaction handle on success. 112 </p> 113 <p> 114 In the case of error, a Tcl error is thrown. 115 </p> 116 </div> 117 <div class="navfooter"> 118 <hr /> 119 <table width="100%" summary="Navigation footer"> 120 <tr> 121 <td width="40%" align="left"><a accesskey="p" href="env_remove.html">Prev</a>��</td> 122 <td width="20%" align="center"> 123 <a accesskey="u" href="tclapi.html">Up</a> 124 </td> 125 <td width="40%" align="right">��<a accesskey="n" href="txn_abort.html">Next</a></td> 126 </tr> 127 <tr> 128 <td width="40%" align="left" valign="top">berkdb envremove��</td> 129 <td width="20%" align="center"> 130 <a accesskey="h" href="index.html">Home</a> 131 </td> 132 <td width="40%" align="right" valign="top">��<span class="emphasis"><em>txn</em></span> abort</td> 133 </tr> 134 </table> 135 </div> 136 </body> 137</html> 138