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     <h3 class="title">
      <a name="innodb-redo-log-buffer">
      </a>
      17.5.4 Log Buffer
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  <p>
   The log buffer is the memory area that holds data to be written to
      the log files on disk. Log buffer size is defined by the
   <a class="link" href="innodb-parameters.html#sysvar_innodb_log_buffer_size">
    <code class="literal">
     innodb_log_buffer_size
    </code>
   </a>
   variable.
      The default size is 64MB. The contents of the log buffer are
      periodically flushed to disk. A large log buffer enables large
      transactions to run without the need to write redo log data to
      disk before the transactions commit. Thus, if you have
      transactions that update, insert, or delete many rows, increasing
      the size of the log buffer saves disk I/O.
  </p>
  <p>
   The
   <a class="link" href="innodb-parameters.html#sysvar_innodb_flush_log_at_trx_commit">
    <code class="literal">
     innodb_flush_log_at_trx_commit
    </code>
   </a>
   variable controls how the contents of the log buffer are written
      and flushed to disk. The
   <a class="link" href="innodb-parameters.html#sysvar_innodb_flush_log_at_timeout">
    <code class="literal">
     innodb_flush_log_at_timeout
    </code>
   </a>
   variable controls log flushing frequency.
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  <p>
   For related information, see
   <a class="xref" href="innodb-init-startup-configuration.html#innodb-startup-memory-configuration" title="Memory Configuration">
    Memory Configuration
   </a>
   , and
   <a class="xref" href="optimizing-innodb-logging.html" title="10.5.4 Optimizing InnoDB Redo Logging">
    Section 10.5.4, “Optimizing InnoDB Redo Logging”
   </a>
   .
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