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📄 BerkeleyDB-Core-Cxx-Txn.pdf(1007.21 KB)
📄 abortresults.html(3.37 KB)
📄 apireq.html(8.15 KB)
📄 architectrecovery.html(25.01 KB)
📄 autocommit.html(7.71 KB)
📄 backuprestore.html(18.35 KB)
📄 blocking_deadlocks.html(32.31 KB)
📄 deadlock.jpg(12.3 KB)
📄 enabletxn.html(45 KB)
📄 envopen.html(7.22 KB)
📄 exclusivelock.html(4.61 KB)
📄 filemanagement.html(14.08 KB)
📄 gettingStarted.css(1.13 KB)
📄 hotfailover.html(8.94 KB)
📄 index.html(18.38 KB)
📄 inmem_txnexample_c.html(21.47 KB)
📄 introduction.html(8.39 KB)
📄 isolation.html(32.43 KB)
📄 lockingsubsystem.html(25.48 KB)
📄 logconfig.html(17.96 KB)
📄 logfileremoval.html(8.78 KB)
📄 maxtxns.html(9.02 KB)
📄 moreinfo.html(6.36 KB)
📄 multithread-intro.html(4.45 KB)
📄 nestedtxn.html(5.97 KB)
📄 nodurabletxn.html(7.83 KB)
📄 perftune-intro.html(4.01 KB)
📄 preface.html(6.63 KB)
📄 readblock.jpg(10.26 KB)
📄 readmodifywrite.html(4.85 KB)
📄 recovery-intro.html(4.7 KB)
📄 recovery.html(11.66 KB)
📄 reversesplit.html(6.29 KB)
📄 rwlocks1-pdf.jpg(187.63 KB)
📄 rwlocks1.jpg(7.25 KB)
📄 simplelock-pdf.jpg(126.26 KB)
📄 simplelock.jpg(4.35 KB)
📄 sysfailure.html(5.7 KB)
📄 txn_ccursor.html(7.34 KB)
📄 txnconcurrency.html(13.8 KB)
📄 txncursor.html(4.68 KB)
📄 txnexample_c.html(27.19 KB)
📄 txnindices.html(5.22 KB)
📄 txnnowait.html(3.48 KB)
📄 usingtxns.html(15.01 KB)
📄 wrapup.html(10.26 KB)
📄 writeblock.jpg(6.22 KB)

Editing: autocommit.html

<?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>Auto Commit</title>
    <link rel="stylesheet" href="gettingStarted.css" type="text/css" />
    <meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
    <link rel="start" href="index.html" title="Getting Started with Berkeley DB Transaction Processing" />
    <link rel="up" href="usingtxns.html" title="Chapter 3. Transaction Basics" />
    <link rel="prev" href="abortresults.html" title="Aborting a Transaction" />
    <link rel="next" href="nestedtxn.html" title="Nested Transactions" />
  </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">Auto Commit</th>
        </tr>
        <tr>
          <td width="20%" align="left"><a accesskey="p" href="abortresults.html">Prev</a> </td>
          <th width="60%" align="center">Chapter 3. Transaction Basics</th>
          <td width="20%" align="right"> <a accesskey="n" href="nestedtxn.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="autocommit"></a>Auto Commit</h2>
          </div>
        </div>
      </div>
      <p>
            While transactions are frequently used to provide atomicity to
            multiple database 
            
            operations, it is sometimes necessary to perform
            a single database 
            
            operation under the control of a transaction.
            Rather than force you to obtain a transaction, perform the single 
            write operation, and then either commit or abort the transaction,
            you can automatically group this sequence of events using
            <span class="emphasis"><em>auto commit</em></span>.
        </p>
      <p>
            To use auto commit:
        </p>
      <div class="orderedlist">
        <ol type="1">
          <li>
            <p>
                        Open your environment and your databases 
                        
                        so that they support
                    transactions.  See <a class="xref" href="enabletxn.html" title="Chapter 2. Enabling Transactions">Enabling Transactions</a> 
                    for details.
                </p>
            <p>
                    Note that frequently auto commit is used for the environment
                    or database open.  To use auto commit for either your
                    environment or database open, specify 
                    <code class="literal">DB_AUTO_COMMIT</code> to the

<code class="methodname">DbEnv::set_flags()</code>
                    or
                    
                    <code class="methodname">Db::open()</code>
                    method. If you specify auto commit for the environment
                    open, then you do not need to also specify auto commit
                    for the database open.
                </p>
          </li>
          <li>
            <p>
                    Do not provide a transactional handle to the method that is
                    performing the database 
                        
                    write operation.
                </p>
          </li>
        </ol>
      </div>
      <p>
            Note that auto commit is not available for cursors. You must always
            open your cursor using a transaction if you want the cursor's
            operations to be transactional protected. See 
            <a class="xref" href="txncursor.html" title="Transactional Cursors">Transactional Cursors</a> for details on using
            transactional cursors.
        </p>
      <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
        <h3 class="title">Note</h3>
        <p>
                Never have more than one active transaction in your thread
                at a time. This is especially a problem if you mix an
                explicit transaction with another operation that uses auto
                commit. Doing so can result in undetectable deadlocks.
            </p>
      </div>
      <p>
            For example, the following uses auto commit to perform the database write operation:
        </p>
      <pre class="programlisting">#include "db_cxx.h"

...

int main(void)
{
    u_int32_t env_flags = DB_CREATE     |  // If the environment does not
                                           // exist, create it.
                          DB_INIT_LOCK  |  // Initialize locking
                          DB_INIT_LOG   |  // Initialize logging
                          DB_INIT_MPOOL |  // Initialize the cache
                          DB_INIT_TXN;     // Initialize transactions

u_int32_t db_flags = DB_CREATE | DB_AUTO_COMMIT;
    Db *dbp = NULL;
    const char *file_name = "mydb.db";
    const char *keystr ="thekey";
    const char *datastr = "thedata";

std::string envHome("/export1/testEnv");
    DbEnv myEnv(0);

try {

myEnv.open(envHome.c_str(), env_flags, 0);
        dbp = new Db(&amp;myEnv, 0);

// Open the database. Note that we are using auto commit for 
        // the open, so the database is able to support transactions.
        dbp-&gt;open(NULL,       // Txn pointer
                  file_name,  // File name
                  NULL,       // Logical db name */
                  DB_BTREE,   // Database type (using btree)
                  db_flags,   // Open flags
                  0);         // File mode. Using defaults

Dbt key, data;
        key.set_data(keystr);
        key.set_size((strlen(keystr) + 1) * sizeof(char));
        key.set_data(datastr);
        key.set_size((strlen(datastr) + 1) * sizeof(char));

// Perform the write. Because the database was opened to support
        // auto commit, this write is performed using auto commit.
        db-&gt;put(NULL, &amp;key, &amp;data, 0);

} catch(DbException &amp;e) {
        std::cerr &lt;&lt; "Error opening database and environment: "
                  &lt;&lt; file_name &lt;&lt; ", "
                  &lt;&lt; envHome &lt;&lt; std::endl;
        std::cerr &lt;&lt; e.what() &lt;&lt; std::endl;
    }

try {
        if (dbp != NULL) 
            dbp-&gt;close(0);
        myEnv.close(0);
    } catch(DbException &amp;e) {
        std::cerr &lt;&lt; "Error closing database and environment: "
                  &lt;&lt; file_name &lt;&lt; ", "
                  &lt;&lt; envHome &lt;&lt; std::endl;
        std::cerr &lt;&lt; e.what() &lt;&lt; std::endl;
        return (EXIT_FAILURE);
    }

return (EXIT_SUCCESS);
} </pre>
    </div>
    <div class="navfooter">
      <hr />
      <table width="100%" summary="Navigation footer">
        <tr>
          <td width="40%" align="left"><a accesskey="p" href="abortresults.html">Prev</a> </td>
          <td width="20%" align="center">
            <a accesskey="u" href="usingtxns.html">Up</a>
          </td>
          <td width="40%" align="right"> <a accesskey="n" href="nestedtxn.html">Next</a></td>
        </tr>
        <tr>
          <td width="40%" align="left" valign="top">Aborting a Transaction </td>
          <td width="20%" align="center">
            <a accesskey="h" href="index.html">Home</a>
          </td>
          <td width="40%" align="right" valign="top"> Nested Transactions</td>
        </tr>
      </table>
    </div>
  </body>
</html>

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