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<title>Berkeley DB Reference Guide: Configuring transactions</title>
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<td><h3><dl><dt>Berkeley DB Reference Guide:<dd>Transaction Subsystem</dl></h3></td>
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<h1 align=center>Configuring transactions</h1>
<p>The application may change the number of simultaneous outstanding
transactions supported by the Berkeley DB environment by calling the
<a href="../../api_c/env_set_tx_max.html">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_c/txn_begin.html">DB_ENV->txn_begin</a> will fail until some active transactions complete.
<p>There is an additional parameter used in configuring transactions; the
<a href="../../api_c/env_set_flags.html#DB_TXN_NOSYNC">DB_TXN_NOSYNC</a> flag. Setting the <a href="../../api_c/env_set_flags.html#DB_TXN_NOSYNC">DB_TXN_NOSYNC</a> flag to
<a href="../../api_c/env_set_flags.html">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>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.
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