1<!--$Id: txn_prepare.so,v 10.35 2004/08/13 03:39:03 bostic Exp $--> 2<!--Copyright (c) 1997,2008 Oracle. All rights reserved.--> 3<!--See the file LICENSE for redistribution information.--> 4<html> 5<head> 6<title>Berkeley DB: DB_TXN->prepare</title> 7<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> 8<meta name="keywords" content="embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++"> 9</head> 10<body bgcolor=white> 11<table width="100%"><tr valign=top> 12<td> 13<b>DB_TXN->prepare</b> 14</td> 15<td align=right> 16<a href="../api_c/api_core.html"><img src="../images/api.gif" alt="API"></a> 17<a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a></td> 18</tr></table> 19<hr size=1 noshade> 20<tt> 21<b><pre> 22#include <db.h> 23<p> 24int 25DB_TXN->prepare(DB_TXN *tid, u_int8_t gid[DB_XIDDATASIZE]); 26</pre></b> 27<hr size=1 noshade> 28<b>Description: DB_TXN->prepare</b> 29<a name="2"><!--meow--></a> 30<p>The DB_TXN->prepare method initiates the beginning of a two-phase commit.</p> 31<p>In a distributed transaction environment, Berkeley DB can be used as a local 32transaction manager. In this case, the distributed transaction manager 33must send <i>prepare</i> messages to each local manager. The local 34manager must then issue a DB_TXN->prepare and await its successful 35return before responding to the distributed transaction manager. Only 36after the distributed transaction manager receives successful responses 37from all of its <i>prepare</i> messages should it issue any 38<i>commit</i> messages.</p> 39<p>In the case of nested transactions, preparing the parent causes all 40unresolved children of the parent transaction to be committed. Child 41transactions should never be explicitly prepared. Their fate will be 42resolved along with their parent's during global recovery.</p> 43<p>The DB_TXN->prepare method 44returns a non-zero error value on failure 45and 0 on success. 46</p> 47<b>Parameters</b> <br> 48 <b>gid</b><ul compact><li>The <b>gid</b> parameter specifies the global transaction ID by which this 49transaction will be known. This global transaction ID will be returned 50in calls to <a href="../api_c/txn_recover.html">DB_ENV->txn_recover</a>, telling the application which global 51transactions must be resolved.</ul> 52<br> 53<hr size=1 noshade> 54<br><b>Class</b> 55<a href="../api_c/env_class.html">DB_ENV</a>, <a href="../api_c/txn_class.html">DB_TXN</a> 56<br><b>See Also</b> 57<a href="../api_c/txn_list.html">Transaction Subsystem and Related Methods</a> 58</tt> 59<table width="100%"><tr><td><br></td><td align=right> 60<a href="../api_c/api_core.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a> 61</td></tr></table> 62<p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font> 63</body> 64</html> 65
