<?xml version="1.0" encoding="UTF-8" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <title>No Wait on Blocks</title> <link rel="stylesheet" href="gettingStarted.css" type="text/css" /> <meta name="generator" content="DocBook XSL Stylesheets V1.62.4" /> <link rel="home" href="index.html" title="Getting Started with Berkeley DB Transaction Processing" /> <link rel="up" href="txnconcurrency.html" title="Chapter 4. Concurrency" /> <link rel="previous" href="readmodifywrite.html" title="Read/Modify/Write" /> <link rel="next" href="reversesplit.html" title="Reverse BTree Splits" /> </head> <body> <div class="navheader"> <table width="100%" summary="Navigation header"> <tr> <th colspan="3" align="center">No Wait on Blocks</th> </tr> <tr> <td width="20%" align="left"><a accesskey="p" href="readmodifywrite.html">Prev</a> </td> <th width="60%" align="center">Chapter 4. Concurrency</th> <td width="20%" align="right"> <a accesskey="n" href="reversesplit.html">Next</a></td> </tr> </table> <hr /> </div> <div class="sect1" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h2 class="title" style="clear: both"><a id="txnnowait"></a>No Wait on Blocks</h2> </div> </div> <div></div> </div> <p> Normally when a DB transaction is blocked on a lock request, it must wait until the requested lock becomes available before its thread-of-control can proceed. However, it is possible to configure a transaction handle such that it will report a deadlock rather than wait for the block to clear. </p> <p> You do this on a transaction by transaction basis by specifying <span> <tt class="literal">DB_TXN_NOWAIT</tt> to the <tt class="methodname">DbEnv::txn_begin()</tt> method. </span> </p> <p> For example: </p> <pre class="programlisting"> DbTxn *txn = NULL; try { envp->txn_begin(NULL, &txn, DB_TXN_NOWAIT); ... } catch (DbException &de) { // Deadlock detection and exception handling omitted // for brevity ...</pre> </div> <div class="navfooter"> <hr /> <table width="100%" summary="Navigation footer"> <tr> <td width="40%" align="left"><a accesskey="p" href="readmodifywrite.html">Prev</a> </td> <td width="20%" align="center"> <a accesskey="u" href="txnconcurrency.html">Up</a> </td> <td width="40%" align="right"> <a accesskey="n" href="reversesplit.html">Next</a></td> </tr> <tr> <td width="40%" align="left" valign="top">Read/Modify/Write </td> <td width="20%" align="center"> <a accesskey="h" href="index.html">Home</a> </td> <td width="40%" align="right" valign="top"> Reverse BTree Splits</td> </tr> </table> </div> </body> </html>