<?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>DbEnv::failchk()</title> <link rel="stylesheet" href="apiReference.css" type="text/css" /> <meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /> <link rel="start" href="index.html" title="Berkeley DB C++ API Reference" /> <link rel="up" href="env.html" title="Chapter 5. The DbEnv Handle" /> <link rel="prev" href="enverr.html" title="DbEnv::err()" /> <link rel="next" href="envfileid_reset.html" title="DbEnv::fileid_reset()" /> </head> <body> <div xmlns="" class="navheader"> <div class="libver"> <p>Library Version 11.2.5.3</p> </div> <table width="100%" summary="Navigation header"> <tr> <th colspan="3" align="center">DbEnv::failchk()</th> </tr> <tr> <td width="20%" align="left"><a accesskey="p" href="enverr.html">Prev</a> </td> <th width="60%" align="center">Chapter 5. The DbEnv Handle </th> <td width="20%" align="right"> <a accesskey="n" href="envfileid_reset.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="envfailchk"></a>DbEnv::failchk()</h2> </div> </div> </div> <pre class="programlisting">#include <db_cxx.h> int DbEnv::failchk(u_int32_t flags);</pre> <p> The <code class="methodname">DbEnv::failchk()</code> method checks for threads of control (either a true thread or a process) that have exited while manipulating Berkeley DB library data structures, while holding a logical database lock, or with an unresolved transaction (that is, a transaction that was never aborted or committed). For more information, see <a href="../../programmer_reference/cam_app.html" class="olink">Architecting Data Store and Concurrent Data Store applications</a>, and <a href="../../programmer_reference/transapp_app.html" class="olink">Architecting Transactional Data Store applications</a>, both in the <em class="citetitle">Berkeley DB Programmer's Reference Guide</em>. </p> <p> The <code class="methodname">DbEnv::failchk()</code> method is used in conjunction with the <a class="xref" href="envset_thread_count.html" title="DbEnv::set_thread_count()">DbEnv::set_thread_count()</a>, <a class="xref" href="envset_isalive.html" title="DbEnv::set_isalive()">DbEnv::set_isalive()</a> and <a class="xref" href="envset_thread_id.html" title="DbEnv::set_thread_id()">DbEnv::set_thread_id()</a> methods. Before calling the <code class="methodname">failchk()</code>method, applications must: </p> <div class="orderedlist"> <ol type="1"> <li> <p> Configure their database using the <a class="xref" href="envset_thread_count.html" title="DbEnv::set_thread_count()">DbEnv::set_thread_count()</a> method. </p> </li> <li> <p> Establish an <code class="literal">is_alive()</code> function and invoke <a class="xref" href="envset_isalive.html" title="DbEnv::set_isalive()">DbEnv::set_isalive()</a> with that function as the <code class="literal">is_alive</code> parameter. </p> </li> <li> <p> Establish a <code class="literal">thread_id</code> function and invoke <a class="xref" href="envset_thread_id.html" title="DbEnv::set_thread_id()">DbEnv::set_thread_id()</a> with that function as the <code class="literal">thread_id</code> parameter. </p> </li> </ol> </div> <p> If any of these methods are omitted, a program may be unable to allocate a thread control block. This is true of the standalone Berkeley DB utility programs. To avoid problems when using the standalone Berkeley DB utility programs with environments configured for failure checking, incorporate the utility's functionality directly in the application, or call the <code class="methodname">DbEnv::failchk()</code> method along with its associated methods before running the utility. </p> <p> If <code class="methodname">DbEnv::failchk()</code> determines a thread of control exited while holding database read locks, it will release those locks. If <code class="methodname">DbEnv::failchk()</code> determines a thread of control exited with an unresolved transaction, the transaction will be aborted. In either of these cases, <code class="methodname">DbEnv::failchk()</code> will return 0 and the application may continue to use the database environment. </p> <p> In either of these cases, the <code class="methodname">DbEnv::failchk()</code> method will also report the process and thread IDs associated with any released locks or aborted transactions. The information is printed to a specified output channel (see the <a class="xref" href="envset_msgfile.html" title="DbEnv::set_msgfile()">DbEnv::set_msgfile()</a> method for more information), or passed to an application callback function (see the <a class="xref" href="envset_msgcall.html" title="DbEnv::set_msgcall()">DbEnv::set_msgcall()</a> method for more information). </p> <p> If <code class="methodname">DbEnv::failchk()</code> determines a thread of control has exited such that database environment recovery is required, it will return <a href="../../programmer_reference/program_errorret.html#program_errorret.DB_RUNRECOVERY" class="olink">DB_RUNRECOVERY</a>. In this case, the application should not continue to use the database environment. For a further description as to the actions the application should take when this failure occurs, see <a href="../../programmer_reference/cam_fail.html" class="olink">Handling failure in Data Store and Concurrent Data Store applications</a>, and <a href="../../programmer_reference/transapp_fail.html" class="olink">Handling failure in Transactional Data Store applications</a>, both in the <em class="citetitle">Berkeley DB Programmer's Reference Guide</em>. </p> <p> In multiprocess applications, it is recommended that the <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handle used to invoke the <code class="methodname">DbEnv::failchk()</code> method not be shared and therefore not <span class="emphasis"><em>free-threaded</em></span>. </p> <p> The <code class="methodname">DbEnv::failchk()</code> method may not be called by the application before the <a class="xref" href="envopen.html" title="DbEnv::open()">DbEnv::open()</a> method is called. </p> <p> The <code class="methodname">DbEnv::failchk()</code> <span> <span> method either returns a non-zero error value or throws an exception that encapsulates a non-zero error value on failure, and returns 0 on success. </span> </span> </p> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="idp1391408"></a>Parameters</h3> </div> </div> </div> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="idp1390760"></a>flags</h4> </div> </div> </div> <p> The <span class="bold"><strong>flags</strong></span> parameter is currently unused, and must be set to 0. </p> </div> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="idp1395936"></a>Errors</h3> </div> </div> </div> <p> The <code class="methodname">DbEnv::failchk()</code> <span> <span> method may fail and throw a <a class="link" href="dbexception.html" title="Chapter 6. The DbException Class">DbException</a> exception, encapsulating one of the following non-zero errors, or return one of the following non-zero errors: </span> </span> </p> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="idp1408352"></a>EINVAL</h4> </div> </div> </div> <p> An invalid flag value or parameter was specified. </p> </div> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="idp1407056"></a>Class</h3> </div> </div> </div> <p> <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> </p> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="idp1409680"></a>See Also</h3> </div> </div> </div> <p> <a class="xref" href="env.html#envlist" title="Database Environments and Related Methods">Database Environments and Related Methods</a> </p> </div> </div> <div class="navfooter"> <hr /> <table width="100%" summary="Navigation footer"> <tr> <td width="40%" align="left"><a accesskey="p" href="enverr.html">Prev</a> </td> <td width="20%" align="center"> <a accesskey="u" href="env.html">Up</a> </td> <td width="40%" align="right"> <a accesskey="n" href="envfileid_reset.html">Next</a></td> </tr> <tr> <td width="40%" align="left" valign="top">DbEnv::err() </td> <td width="20%" align="center"> <a accesskey="h" href="index.html">Home</a> </td> <td width="40%" align="right" valign="top"> DbEnv::fileid_reset()</td> </tr> </table> </div> </body> </html>