<?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::set_app_dispatch()</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="envset_alloc.html" title="DbEnv::set_alloc()" /> <link rel="next" href="envset_backup_callbacks.html" title="DbEnv::set_backup_callbacks()" /> </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::set_app_dispatch()</th> </tr> <tr> <td width="20%" align="left"><a accesskey="p" href="envset_alloc.html">Prev</a> </td> <th width="60%" align="center">Chapter 5. The DbEnv Handle </th> <td width="20%" align="right"> <a accesskey="n" href="envset_backup_callbacks.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="envset_app_dispatch"></a>DbEnv::set_app_dispatch()</h2> </div> </div> </div> <pre class="programlisting">#include <db_cxx.h> int DbEnv::set_app_dispatch(int (*tx_recover)(DbEnv *dbenv, Dbt *log_rec, DbLsn *lsn, db_recops op));</pre> <p> Declare a function to be called during transaction abort and recovery to process application-specific log records. </p> <p> The <code class="methodname">DbEnv::set_app_dispatch()</code> method configures operations performed using the specified <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handle, not all operations performed on the underlying database environment. </p> <p> The <code class="methodname">DbEnv::set_app_dispatch()</code> method may not be called after the <a class="xref" href="envopen.html" title="DbEnv::open()">DbEnv::open()</a> method is called. If the database environment already exists when <a class="xref" href="envopen.html" title="DbEnv::open()">DbEnv::open()</a> is called, the information specified to <code class="methodname">DbEnv::set_app_dispatch()</code> must be consistent with the existing environment or corruption can occur. </p> <p> The <code class="methodname">DbEnv::set_app_dispatch()</code> method returns a non-zero error value on failure and 0 on success. </p> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="idp7101480"></a>Parameters</h3> </div> </div> </div> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="idp7131392"></a>tx_recover</h4> </div> </div> </div> <p> The <span class="bold"><strong>tx_recover</strong></span> parameter is the application's abort and recovery function. The function takes four parameters: </p> <div class="itemizedlist"> <ul type="disc"> <li> <p> <code class="literal">dbenv</code> </p> <p> The <span class="bold"><strong>dbenv</strong></span> parameter is the enclosing database environment handle. </p> </li> <li> <p> <code class="literal">log_rec</code> </p> <p> The <span class="bold"><strong>log_rec</strong></span> parameter is a log record. </p> </li> <li> <p> <code class="literal">lsn</code> </p> <p> The <span class="bold"><strong>lsn</strong></span> parameter is a log sequence number. </p> </li> <li> <p> <code class="literal">op</code> </p> <p> The <span class="bold"><strong>op</strong></span> parameter is one of the following values: </p> <div class="itemizedlist"> <ul type="circle"> <li> <p><a id="set_app_dispatch_DB_TXN_BACKWARD_ROLL"></a> <code class="literal">DB_TXN_BACKWARD_ROLL</code> </p> <p> The log is being read backward to determine which transactions have been committed and to abort those operations that were not; undo the operation described by the log record. </p> </li> <li> <p><a id="set_app_dispatch_DB_TXN_FORWARD_ROLL"></a> <code class="literal">DB_TXN_FORWARD_ROLL</code> </p> <p> The log is being played forward; redo the operation described by the log record. </p> </li> <li> <p><a id="set_app_dispatch_DB_TXN_ABORT"></a> <code class="literal">DB_TXN_ABORT</code> </p> <p> The log is being read backward during a transaction abort; undo the operation described by the log record. </p> </li> <li> <p><a id="set_app_dispatch_DB_TXN_APPLY"></a> <code class="literal">DB_TXN_APPLY</code> </p> <p> The log is being applied on a replica site; redo the operation described by the log record. </p> </li> <li> <p><a id="set_app_dispatch_DB_TXN_PRINT"></a> <code class="literal">DB_TXN_PRINT</code> </p> <p> The log is being printed for debugging purposes; print the contents of this log record in the desired format. </p> </li> </ul> </div> <p> The DB_TXN_FORWARD_ROLL and DB_TXN_APPLY operations frequently imply the same actions, redoing changes that appear in the log record, although if a recovery function is to be used on a replication client where reads may be taking place concurrently with the processing of incoming messages, DB_TXN_APPLY operations should also perform appropriate locking. The macro DB_REDO(op) checks that the operation is one of DB_TXN_FORWARD_ROLL or DB_TXN_APPLY, and should be used in the recovery code to refer to the conditions under which operations should be redone. Similarly, the macro DB_UNDO(op) checks if the operation is one of DB_TXN_BACKWARD_ROLL or DB_TXN_ABORT. </p> </li> </ul> </div> <p> The function must return 0 on success and either <span class="bold"><strong>errno</strong></span> or a value outside of the Berkeley DB error name space on failure. </p> </div> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="idp7150096"></a>Errors</h3> </div> </div> </div> <p> The <code class="methodname">DbEnv::set_app_dispatch()</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="idp7147040"></a>EINVAL</h4> </div> </div> </div> <p> If the method was called after <a class="xref" href="envopen.html" title="DbEnv::open()">DbEnv::open()</a> was called; or if 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="idp7160048"></a>Class</h3> </div> </div> </div> <p> <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a>, <a class="link" href="txn.html" title="Chapter 13. The DbTxn Handle">DbTxn</a> </p> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="idp7132544"></a>See Also</h3> </div> </div> </div> <p> <a class="xref" href="txn.html#txnlist" title="Transaction Subsystem and Related Methods">Transaction Subsystem 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="envset_alloc.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="envset_backup_callbacks.html">Next</a></td> </tr> <tr> <td width="40%" align="left" valign="top">DbEnv::set_alloc() </td> <td width="20%" align="center"> <a accesskey="h" href="index.html">Home</a> </td> <td width="40%" align="right" valign="top"> DbEnv::set_backup_callbacks()</td> </tr> </table> </div> </body> </html>