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14<b><i>txn</i> <b>commit</b></b>
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22<b><pre>txn commit
23	[-nosync]
24	[-sync]
25</pre></b>
26<b>Description(txn commit)</b>
27<p>The <i>txn</i> <b>commit</b> command ends the transaction.</p>
28<p>In the case of nested transactions, if the transaction is a parent
29transaction with unresolved (neither committed or aborted) child
30transactions, the child transactions are aborted and the commit of the
31parent will succeed.</p>
32<p>In the case of nested transactions, if the transaction is a child
33transaction, its locks are not released, but are acquired by its parent.
34Although the commit of the child transaction will succeed, the actual
35resolution of the child transaction is postponed until the parent
36transaction is committed or aborted; that is, if its parent transaction
37commits, it will be committed, and if its parent transaction aborts, it
38will be aborted.</p>
39<p>If the <b>-nosync</b> option is not specified, a commit log record is
40written and flushed to disk, as are all previously written log records.</p>
41<p>The options are as follows:</p>
42<br>
43<b>-nosync</b><ul compact><li>Do not synchronously flush the log. This means the transaction will
44exhibit the ACI (atomicity, consistency, and isolation) properties, but
45not D (durability); that is, database integrity will be maintained, but
46it is possible that this transaction may be undone during recovery
47instead of being redone.
48<p>This behavior may be set for an entire Berkeley DB environment as part of
49the <b>berkdb env</b> call.</p></ul>
50<b>-sync</b><ul compact><li>Synchronously flush the log. This means the transaction will exhibit
51all of the ACID (atomicity, consistency, isolation and durability)
52properties.
53<p>This behavior is the default for Berkeley DB environments unless the
54<b>-nosync</b> option was specified to the <b>berkdb env</b> or
55<i>env</i> <b>txn</b> calls.</p></ul>
56<br>
57<p>After <i>txn</i> <b>commit</b> has been called, regardless of its return, the
58<b>txn</b> handle may not be accessed again.  If <i>txn</i> <b>commit</b>
59encounters an error, this transaction and all child transactions of this
60transaction are aborted.</p>
61<p>The <i>txn</i> <b>commit</b> command returns 0 on success, and in the case of error, a Tcl error
62is thrown.</p>
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