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<h2 class="title" style="clear: both"><a id="set_lg_bsize_parameter"></a>set_lg_bsize</h2>
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<p>
Sets the size of the in-memory log buffer, in bytes.
</p>
<p>
For the DB, when the logging subsystem is configured for on-disk logging, the
default size of the in-memory log buffer is approximately 32KB.
For the BDB SQL interface, when the logging subsystem is configured for on-disk logging, the
default size of the in-memory log buffer is approximately 64KB. Log
information is stored in-memory until the storage space fills up or
a 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 syntax of this parameter in the <code class="literal">DB_CONFIG</code> file is
a single line with the string <code class="literal">set_lg_bsize</code>,
one or more whitespace characters, and the log buffer size in bytes.
</p>
<p>
If the database environment already exists when this parameter is
changed, it is ignored. To change this value after the environment
has been created, re-create your environment as described in <a href="../../bdb-sql/using_dbconfig.html#using_dbconfig.title" class="olink">the DB_CONFIG File</a>.
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<p>For more information, see <a class="xref" href="envset_lg_bsize.html" title="DbEnv::set_lg_bsize()">DbEnv::set_lg_bsize()</a>. </p>
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