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diff --git a/db/docs/gsg_txn/C/nestedtxn.html b/db/docs/gsg_txn/C/nestedtxn.html new file mode 100644 index 000000000..c202d794d --- /dev/null +++ b/db/docs/gsg_txn/C/nestedtxn.html @@ -0,0 +1,140 @@ +<?xml version="1.0" encoding="ISO-8859-1" standalone="no"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml"> + <head> + <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" /> + <title>Nested Transactions</title> + <link rel="stylesheet" href="gettingStarted.css" type="text/css" /> + <meta name="generator" content="DocBook XSL Stylesheets V1.62.4" /> + <link rel="home" href="index.html" title="Getting Started with Berkeley DB Transaction Processing" /> + <link rel="up" href="usingtxns.html" title="Chapter 3. Transaction Basics" /> + <link rel="previous" href="autocommit.html" title="Auto Commit" /> + <link rel="next" href="txncursor.html" title="Transactional Cursors" /> + </head> + <body> + <div class="navheader"> + <table width="100%" summary="Navigation header"> + <tr> + <th colspan="3" align="center">Nested Transactions</th> + </tr> + <tr> + <td width="20%" align="left"><a accesskey="p" href="autocommit.html">Prev</a> </td> + <th width="60%" align="center">Chapter 3. Transaction Basics</th> + <td width="20%" align="right"> <a accesskey="n" href="txncursor.html">Next</a></td> + </tr> + </table> + <hr /> + </div> + <div class="sect1" lang="en" xml:lang="en"> + <div class="titlepage"> + <div> + <div> + <h2 class="title" style="clear: both"><a id="nestedtxn"></a>Nested Transactions</h2> + </div> + </div> + <div></div> + </div> + <p> + A <span class="emphasis"><em>nested transaction</em></span> is used to provide a + transactional guarantee for a subset of operations performed within + the scope of a larger transaction. Doing this allows you to commit + and abort the subset of operations independently of the larger + transaction. + </p> + <p> + The rules to the usage of a nested transaction are as follows: + </p> + <div class="itemizedlist"> + <ul type="disc"> + <li> + <p> + While the nested (child) transaction is active, the parent + transaction may not perform any operations other than to commit + or abort, or to create more child transactions. + </p> + </li> + <li> + <p> + Committing a nested transaction has no effect on the state + of the parent transaction. The parent transaction is still + uncommitted. However, the parent transaction can now + see any modifications made by the child transaction. + Those modifications, of course, are still hidden to all + other transactions until the parent also commits. + </p> + </li> + <li> + <p> + Likewise, aborting the nested transaction has no effect on + the state of the parent transaction. The only result of the + abort is that neither the parent nor any + other transactions will see any of the + database modifications performed under the protection of the + nested transaction. + </p> + </li> + <li> + <p> + If the parent transaction commits or aborts while it has + active children, the child transactions are resolved in the + same way as the parent. That is, if the parent aborts, then + the child transactions abort as well. If the parent commits, + then whatever modifications have been performed by the child + transactions are also committed. + </p> + </li> + <li> + <p> + The locks held by a nested transaction are not released when + that transaction commits. Rather, they are now held by the + parent transaction until such a time as that parent commits. + </p> + </li> + <li> + <p> + Any database modifications performed by the nested transaction + are not visible outside of the larger encompassing + transaction until such a time as that parent transaction is + committed. + </p> + </li> + <li> + <p> + The depth of the nesting that you can achieve with nested + transaction is limited only by memory. + </p> + </li> + </ul> + </div> + <p> + To create a nested transaction, simply pass the parent transaction's + handle when you created the nested transaction's handle. For + example: + </p> + <pre class="programlisting"> /* parent transaction */ + DB_TXN *parent_txn, *child_txn; + ret = envp->txn_begin(envp, NULL, &parent_txn, 0); + /* child transaction */ + ret = envp->txn_begin(envp, parent_txn, &child_txn, 0); </pre> + </div> + <div class="navfooter"> + <hr /> + <table width="100%" summary="Navigation footer"> + <tr> + <td width="40%" align="left"><a accesskey="p" href="autocommit.html">Prev</a> </td> + <td width="20%" align="center"> + <a accesskey="u" href="usingtxns.html">Up</a> + </td> + <td width="40%" align="right"> <a accesskey="n" href="txncursor.html">Next</a></td> + </tr> + <tr> + <td width="40%" align="left" valign="top">Auto Commit </td> + <td width="20%" align="center"> + <a accesskey="h" href="index.html">Home</a> + </td> + <td width="40%" align="right" valign="top"> Transactional Cursors</td> + </tr> + </table> + </div> + </body> +</html> |