mirror of
https://github.com/berkeleydb/libdb.git
synced 2024-11-16 17:16:25 +00:00
91 lines
4.5 KiB
HTML
91 lines
4.5 KiB
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>Configuring transactions</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="Berkeley DB Programmer's Reference Guide" />
|
||
<link rel="up" href="txn.html" title="Chapter 19. The Transaction Subsystem" />
|
||
<link rel="prev" href="txn.html" title="Chapter 19. The Transaction Subsystem" />
|
||
<link rel="next" href="txn_limits.html" title="Transaction limits" />
|
||
</head>
|
||
<body>
|
||
<div xmlns="" class="navheader">
|
||
<div class="libver">
|
||
<p>Library Version 11.2.5.2</p>
|
||
</div>
|
||
<table width="100%" summary="Navigation header">
|
||
<tr>
|
||
<th colspan="3" align="center">Configuring transactions</th>
|
||
</tr>
|
||
<tr>
|
||
<td width="20%" align="left"><a accesskey="p" href="txn.html">Prev</a> </td>
|
||
<th width="60%" align="center">Chapter 19.
|
||
The Transaction Subsystem
|
||
</th>
|
||
<td width="20%" align="right"> <a accesskey="n" href="txn_limits.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="txn_config"></a>Configuring transactions</h2>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<p>The application may change the number of simultaneous outstanding
|
||
transactions supported by the Berkeley DB environment by calling the
|
||
<a href="../api_reference/C/envset_tx_max.html" class="olink">DB_ENV->set_tx_max()</a> method. This will also set the size of the
|
||
underlying transaction subsystem's region. When the number of
|
||
outstanding transactions is reached, additional calls to
|
||
<a href="../api_reference/C/txnbegin.html" class="olink">DB_ENV->txn_begin()</a> will fail until some active transactions complete.</p>
|
||
<p>The application can limit how long a transaction runs or blocks on
|
||
contested resources.
|
||
The <a href="../api_reference/C/envset_timeout.html" class="olink">DB_ENV->set_timeout()</a> method specifies the length of the timeout.
|
||
This value is checked whenever deadlock detection is performed or
|
||
when the transaction is about to block on a lock that cannot be
|
||
immediately granted.
|
||
Because timeouts are only checked at these times, the accuracy of the
|
||
timeout depends on how often deadlock detection is performed or how
|
||
frequently the transaction blocks.</p>
|
||
<p>There is an additional parameter used in configuring transactions; the
|
||
<a href="../api_reference/C/envset_flags.html#envset_flags_DB_TXN_NOSYNC" class="olink">DB_TXN_NOSYNC</a>. Setting the <a href="../api_reference/C/envset_flags.html#envset_flags_DB_TXN_NOSYNC" class="olink">DB_TXN_NOSYNC</a> flag to
|
||
<a href="../api_reference/C/envset_flags.html" class="olink">DB_ENV->set_flags()</a> when opening a transaction region changes the
|
||
behavior of transactions to not write or synchronously flush the log
|
||
during transaction commit.</p>
|
||
<p>This change may significantly increase application transactional
|
||
throughput. However, it means that although transactions will continue
|
||
to exhibit the ACI (atomicity, consistency, and isolation) properties,
|
||
they will not have D (durability). Database integrity will be
|
||
maintained, but it is possible that some number of the most recently
|
||
committed transactions may be undone during recovery instead of being
|
||
redone.</p>
|
||
</div>
|
||
<div class="navfooter">
|
||
<hr />
|
||
<table width="100%" summary="Navigation footer">
|
||
<tr>
|
||
<td width="40%" align="left"><a accesskey="p" href="txn.html">Prev</a> </td>
|
||
<td width="20%" align="center">
|
||
<a accesskey="u" href="txn.html">Up</a>
|
||
</td>
|
||
<td width="40%" align="right"> <a accesskey="n" href="txn_limits.html">Next</a></td>
|
||
</tr>
|
||
<tr>
|
||
<td width="40%" align="left" valign="top">Chapter 19.
|
||
The Transaction Subsystem
|
||
</td>
|
||
<td width="20%" align="center">
|
||
<a accesskey="h" href="index.html">Home</a>
|
||
</td>
|
||
<td width="40%" align="right" valign="top"> Transaction limits</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</body>
|
||
</html>
|