1<!--$Id: txn.so,v 11.17 2003/10/18 19:16:24 bostic Exp $--> 2<!--$Id: m4.tcl,v 11.28 2004/12/16 19:13:05 bostic Exp $--> 3<!--Copyright (c) 1997,2008 Oracle. All rights reserved.--> 4<!--See the file LICENSE for redistribution information.--> 5<html> 6<head> 7<title>Berkeley DB: env txn</title> 8<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> 9<meta name="keywords" content="embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++"> 10</head> 11<body bgcolor=white> 12<table width="100%"><tr valign=top> 13<td> 14<b><i>env</i> <b>txn</b></b> 15</td> 16<td align=right> 17<a href="/api_tcl/api_tcl.html"><img src="/images/api.gif" alt="API"></a> 18<a href="/ref/toc.html"><img src="/images/ref.gif" alt="Ref"></a></td> 19</tr></table> 20<hr size=1 noshade> 21<tt> 22<b><pre>env txn 23 [-nosync] 24 [-nowait] 25 [-parent txnid] 26 [-sync] 27</pre></b> 28<b>Description(env txn)</b> 29<p>The <i>env</i> <b>txn</b> command begins a transaction. The returned transaction 30handle is bound to a Tcl command of the form <b>env.txnX</b>, where 31X is an integer starting at 0 (for example, env0.txn0 and env0.txn1). 32It is through this Tcl command that the script accesses the transaction 33methods.</p> 34<p>The options are as follows:</p> 35<br> 36<b>-nosync</b><ul compact><li>Do not synchronously flush the log when this transaction commits or 37prepares. This means the transaction will exhibit the ACI (atomicity, 38consistency, and isolation) properties, but not D (durability); that 39is, database integrity will be maintained, but it is possible that this 40transaction may be undone during recovery instead of being redone. 41<p>This behavior may be set for an entire Berkeley DB environment as part of the 42<b>berkdb env</b> call.</p></ul> 43<b>-nowait</b><ul compact><li>If a lock is unavailable for any Berkeley DB operation performed in the context 44of this transaction, throw a Tcl error immediately instead of blocking on 45the lock.</ul> 46<b>-parent txnid</b><ul compact><li>Create the new transaction as a nested transaction, with the specified 47transaction indicated as its parent. Transactions may be nested to any 48level.</ul> 49<b>-sync</b><ul compact><li>Synchronously flush the log when this transaction commits or prepares. 50This means the transaction will exhibit all of the ACID (atomicity, 51consistency, isolation, and durability) properties. 52<p>This behavior is the default for Berkeley DB environments unless the 53<b>-nosync</b> option was specified to the <b>berkdb env</b> call.</p></ul> 54<br> 55<p>The <i>env</i> <b>txn</b> command returns a transaction handle on success.</p> 56<p>In the case of error, a Tcl error is thrown.</p> 57</tt> 58<table width="100%"><tr><td><br></td><td align=right> 59<a href="/api_tcl/api_tcl.html"><img src="/images/api.gif" alt="API"></a><a href="/ref/toc.html"><img src="/images/ref.gif" alt="Ref"></a> 60</td></tr></table> 61<p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font> 62</body> 63</html> 64