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140 lines
5.7 KiB
HTML
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>env txn</title>
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<link rel="stylesheet" href="apiReference.css" type="text/css" />
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<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
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<link rel="start" href="index.html" title="Berkeley DB TCL API Reference" />
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<link rel="up" href="tclapi.html" title="Chapter 1. Berkeley DB Tcl APIs" />
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<link rel="prev" href="env_remove.html" title="berkdb envremove" />
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<div xmlns="" class="navheader">
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<div class="libver">
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<p>Library Version 11.2.5.2</p>
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</div>
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<table width="100%" summary="Navigation header">
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<tr>
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<th colspan="3" align="center"><span xmlns="http://www.w3.org/1999/xhtml" class="emphasis"><em>env</em></span> txn</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="env_remove.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 1.
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Berkeley DB Tcl APIs
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="txn_abort.html">Next</a></td>
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</tr>
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</table>
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<hr />
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</div>
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<div class="sect1" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h2 class="title" style="clear: both"><a id="txn"></a><span class="emphasis"><em>env</em></span> txn</h2>
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</div>
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</div>
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</div>
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<pre class="programlisting">env txn
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[-nosync]
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[-nowait]
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[-parent txnid]
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[-sync] </pre>
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<p>
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The <span class="emphasis"><em>env</em></span> <span class="bold"><strong>txn</strong></span>
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command begins a transaction. The returned transaction handle is
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bound to a Tcl command of the form <span class="bold"><strong>env.txnX</strong></span>, where X is an integer starting at 0
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(for example, env0.txn0 and env0.txn1). It is through this Tcl command
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that the script accesses the transaction methods.
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</p>
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<p>
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The options are as follows:
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</p>
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<div class="itemizedlist">
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<ul type="disc">
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<li>
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<p>
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<span class="bold"><strong>-nosync</strong></span>
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</p>
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<p>
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Do not synchronously flush the log when this transaction commits or
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prepares. This means the transaction will exhibit the ACI (atomicity,
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consistency, and isolation) properties, but not D (durability); that
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is, database integrity will be maintained, but it is possible that
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this transaction may be undone during recovery instead of being
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redone.
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</p>
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<p>
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This behavior may be set for an entire Berkeley DB environment as part
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of the <span class="bold"><strong>berkdb env</strong></span> call.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>-nowait</strong></span>
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</p>
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<p>
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If a lock is unavailable for any Berkeley DB operation performed in
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the context of this transaction, throw a Tcl error immediately instead
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of blocking on the lock.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>-parent txnid</strong></span>
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</p>
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<p>
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Create the new transaction as a nested transaction, with the specified
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transaction indicated as its parent. Transactions may be nested to
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any level.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>-sync</strong></span>
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</p>
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<p>
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Synchronously flush the log when this transaction commits or prepares.
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This means the transaction will exhibit all of the ACID (atomicity,
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consistency, isolation, and durability) properties.
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</p>
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<p>
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This behavior is the default for Berkeley DB environments unless the
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<span class="bold"><strong>-nosync</strong></span> option was specified to the
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<span class="bold"><strong>berkdb env</strong></span> call.
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</p>
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</li>
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</ul>
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</div>
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<p>
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The <span class="emphasis"><em>env</em></span> <span class="bold"><strong>txn</strong></span>
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command returns a transaction handle on success.
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</p>
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<p>
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In the case of error, a Tcl error is thrown.
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</p>
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</div>
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<div class="navfooter">
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<hr />
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<table width="100%" summary="Navigation footer">
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<tr>
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<td width="40%" align="left"><a accesskey="p" href="env_remove.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="tclapi.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="txn_abort.html">Next</a></td>
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</tr>
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<tr>
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<td width="40%" align="left" valign="top">berkdb envremove </td>
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<td width="20%" align="center">
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<a accesskey="h" href="index.html">Home</a>
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</td>
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<td width="40%" align="right" valign="top"> <span class="emphasis"><em>txn</em></span> abort</td>
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</tr>
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</table>
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</div>
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</body>
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</html>
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