1 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
3 <html xmlns="http://www.w3.org/1999/xhtml">
5 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
6 <title>set_lg_bsize</title>
7 <link rel="stylesheet" href="apiReference.css" type="text/css" />
8 <meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
9 <link rel="start" href="index.html" title="Berkeley DB C++ API Reference" />
10 <link rel="up" href="configuration_reference.html" title="Appendix B. DB_CONFIG Parameter Reference" />
11 <link rel="prev" href="set_intermediate_dir_mode_parameter.html" title="set_intermediate_dir_mode" />
12 <link rel="next" href="set_lg_dir_parameter.html" title="set_lg_dir" />
15 <div xmlns="" class="navheader">
17 <p>Library Version 11.2.5.3</p>
19 <table width="100%" summary="Navigation header">
21 <th colspan="3" align="center">set_lg_bsize</th>
24 <td width="20%" align="left"><a accesskey="p" href="set_intermediate_dir_mode_parameter.html">Prev</a> </td>
25 <th width="60%" align="center">Appendix B. DB_CONFIG Parameter Reference</th>
26 <td width="20%" align="right"> <a accesskey="n" href="set_lg_dir_parameter.html">Next</a></td>
31 <div class="sect1" lang="en" xml:lang="en">
32 <div class="titlepage">
35 <h2 class="title" style="clear: both"><a id="set_lg_bsize_parameter"></a>set_lg_bsize</h2>
40 Sets the size of the in-memory log buffer, in bytes.
43 For the DB, when the logging subsystem is configured for on-disk logging, the
44 default size of the in-memory log buffer is approximately 32KB.
45 For the BDB SQL interface, when the logging subsystem is configured for on-disk logging, the
46 default size of the in-memory log buffer is approximately 64KB. Log
47 information is stored in-memory until the storage space fills up or
48 a transaction commit forces the information to be flushed to stable
49 storage. In the presence of long-running transactions or transactions
50 producing large amounts of data, larger buffer sizes can increase
54 When the logging subsystem is configured for in-memory logging, the
55 default size of the in-memory log buffer is 1MB. Log information is
56 stored in-memory until the storage space fills up or transaction abort
57 or commit frees up the memory for new transactions. In the presence
58 of long-running transactions or transactions producing large amounts
59 of data, the buffer size must be sufficient to hold all log
60 information that can accumulate during the longest running
61 transaction. When choosing log buffer and file sizes for in-memory
62 logs, applications should ensure the in-memory log buffer size is
63 large enough that no transaction will ever span the entire buffer, and
64 avoid a state where the in-memory buffer is full and no space can be
65 freed because a transaction that started in the first log "file" is
69 The syntax of this parameter in the <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> file is a
70 single line with the string
71 <code class="literal">set_lg_bsize</code>, one or more whitespace
72 characters, and the log buffer size in bytes.
75 If the database environment already exists when this parameter is
76 changed, it is ignored. To change this value after the environment
77 has been created, re-create your environment.
80 For more information, see <a class="xref" href="envset_lg_bsize.html" title="DbEnv::set_lg_bsize()">DbEnv::set_lg_bsize()</a>.
83 <div class="navfooter">
85 <table width="100%" summary="Navigation footer">
87 <td width="40%" align="left"><a accesskey="p" href="set_intermediate_dir_mode_parameter.html">Prev</a> </td>
88 <td width="20%" align="center">
89 <a accesskey="u" href="configuration_reference.html">Up</a>
91 <td width="40%" align="right"> <a accesskey="n" href="set_lg_dir_parameter.html">Next</a></td>
94 <td width="40%" align="left" valign="top">set_intermediate_dir_mode </td>
95 <td width="20%" align="center">
96 <a accesskey="h" href="index.html">Home</a>
98 <td width="40%" align="right" valign="top"> set_lg_dir</td>