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<h2 class="title" style="clear: both"><a id="envset_lg_bsize"></a>DbEnv::set_lg_bsize()</h2>
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<pre class="programlisting">#include <db_cxx.h>
int
DbEnv::set_lg_bsize(u_int32_t lg_bsize); </pre>
<p>
Set the size of the in-memory log buffer, in bytes.
</p>
<p>
When the logging subsystem is configured for on-disk logging, the
default size of the in-memory log buffer is approximately 32KB. Log
information is stored in-memory until the storage space fills up or
transaction commit forces the information to be flushed to stable
storage. In the presence of long-running transactions or transactions
producing large amounts of data, larger buffer sizes can increase
throughput.
</p>
<p>
When the logging subsystem is configured for in-memory logging, the
default size of the in-memory log buffer is 1MB. Log information is
stored in-memory until the storage space fills up or transaction abort
or commit frees up the memory for new transactions. In the presence
of long-running transactions or transactions producing large amounts
of data, the buffer size must be sufficient to hold all log
information that can accumulate during the longest running
transaction. When choosing log buffer and file sizes for in-memory
logs, applications should ensure the in-memory log buffer size is
large enough that no transaction will ever span the entire buffer, and
avoid a state where the in-memory buffer is full and no space can be
freed because a transaction that started in the first log "file" is
still active.
</p>
<p>
The database environment's log buffer size may also be configured
using the environment's <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> file. The
syntax of the entry in that file is a single line with the string
"set_lg_bsize", one or more whitespace characters, and the size in
bytes. Because the <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> file is
read when the database environment is opened, it will silently
overrule configuration done before that time.
</p>
<p>
The <code class="methodname">DbEnv::set_lg_bsize()</code> method configures a database environment,
not only operations performed using the specified <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handle.
</p>
<p>
The <code class="methodname">DbEnv::set_lg_bsize()</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_lg_bsize()</code> will be ignored.
</p>
<p>
The <code class="methodname">DbEnv::set_lg_bsize()</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="id1687777"></a>Parameters</h3>
</div>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="id1687838"></a>lg_bsize</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>lg_bsize</strong></span> parameter is the size of
the in-memory log buffer, in bytes.
</p>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="id1687923"></a>Errors</h3>
</div>
</div>
</div>
<p>
The <code class="methodname">DbEnv::set_lg_bsize()</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="id1687920"></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="id1687810"></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="logc.html" title="The DbLogc Handle">DbLogc</a>,
<a class="link" href="lsn.html" title="Chapter 8. The DbLsn Handle">DbLsn</a>
</p>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="id1687943"></a>See Also</h3>
</div>
</div>
</div>
<p>
<a class="xref" href="lsn.html#loglist" title="Logging Subsystem and Related Methods">Logging Subsystem and Related Methods</a>
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