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<a NAME="Transaction Commands"></a>Transaction Commands</h2>
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Transactions are used in a manner similar to the other subsystems.
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We create a handle to the transaction and then use it for a variety
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of operations. Some of the transaction commands use the environment
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instead. Those are presented first. The transaction command
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handle returned is the handle used by the various commands that can be
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transaction protected, such as <a href="../../docs/api_tcl/db_cursor.html">cursors</a>.
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<p><b>> <env> txn_checkpoint [-kbyte <i>kb</i>] [-min <i>min</i>]</b>
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<p>This command causes a checkpoint of the transaction region. It
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is a direct translation of the <a href="../../docs/api_c/txn_checkpoint.html">txn_checkpoint
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It returns either a 0 (for success), a DB error message or it throws a
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Tcl error with a system message. The arguments are:
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<b>-kbyte </b>causes the checkpoint to occur only if <b><i>kb</i></b> kilobytes
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of log data has been written since the last checkpoint</li>
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<b>-min</b> causes the checkpoint to occur only if <b><i>min</i></b> minutes
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have passed since the last checkpoint</li>
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<br><b>> <env> txn_stat</b>
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<p>This command returns transaction statistics. It is a direct translation
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of the <a href="../../docs/api_c/txn_stat.html">txn_stat</a> function.
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It will return a list of name/value pairs that correspond to the DB_TXN_STAT
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<br><b>> <env> txn_id_set </b><i> current max</i>
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<p>This is a diagnosic command that sets the next transaction id to be
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allocated and the maximum transaction
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<br>id, which is the point at which the relcaimation algorthm is triggered.
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<br><b>> <txn> id</b>
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<p>This command returns the transaction id. It is a direct call to
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the <a href="../../docs/api_c/txn_id.html">txn_id</a> function. The
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typical use of this identifier is as the <b><i>locker</i></b> value for
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the <a href="lock.html">lock_get</a> and <a href="lock.html">lock_vec</a>
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<br><b>> <txn> prepare</b>
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<p>This command initiates a two-phase commit. It is a direct call
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to the <a href="../../docs/api_c/txn_prepare.html">txn_prepare</a> function.
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It returns either a 0 (for success), a DB error message or it throws a
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Tcl error with a system message.
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<hr WIDTH="100%"><a NAME="> <env> lock_vec"></a><b>> <env> txn_timeout
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<p>This command sets thetransaction timeout for transactions started in
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the future in this environment. The timeout is in micorseconds.