<!--$Id: txn.so,v 11.17 2003/10/18 19:16:24 bostic Exp $--> <!--$Id: m4.tcl,v 11.28 2004/12/16 19:13:05 bostic Exp $--> <!--Copyright (c) 1997,2008 Oracle. All rights reserved.--> <!--See the file LICENSE for redistribution information.--> <html> <head> <title>Berkeley DB: env txn</title> <meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> <meta name="keywords" content="embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++"> </head> <body bgcolor=white> <table width="100%"><tr valign=top> <td> <b><i>env</i> <b>txn</b></b> </td> <td align=right> <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></td> </tr></table> <hr size=1 noshade> <tt> <b><pre>env txn [-nosync] [-nowait] [-parent txnid] [-sync] </pre></b> <b>Description(env txn)</b> <p>The <i>env</i> <b>txn</b> command begins a transaction. The returned transaction handle is bound to a Tcl command of the form <b>env.txnX</b>, where X is an integer starting at 0 (for example, env0.txn0 and env0.txn1). It is through this Tcl command that the script accesses the transaction methods.</p> <p>The options are as follows:</p> <br> <b>-nosync</b><ul compact><li>Do not synchronously flush the log when this transaction commits or prepares. This means the transaction will exhibit the ACI (atomicity, consistency, and isolation) properties, but not D (durability); that is, database integrity will be maintained, but it is possible that this transaction may be undone during recovery instead of being redone. <p>This behavior may be set for an entire Berkeley DB environment as part of the <b>berkdb env</b> call.</p></ul> <b>-nowait</b><ul compact><li>If a lock is unavailable for any Berkeley DB operation performed in the context of this transaction, throw a Tcl error immediately instead of blocking on the lock.</ul> <b>-parent txnid</b><ul compact><li>Create the new transaction as a nested transaction, with the specified transaction indicated as its parent. Transactions may be nested to any level.</ul> <b>-sync</b><ul compact><li>Synchronously flush the log when this transaction commits or prepares. This means the transaction will exhibit all of the ACID (atomicity, consistency, isolation, and durability) properties. <p>This behavior is the default for Berkeley DB environments unless the <b>-nosync</b> option was specified to the <b>berkdb env</b> call.</p></ul> <br> <p>The <i>env</i> <b>txn</b> command returns a transaction handle on success.</p> <p>In the case of error, a Tcl error is thrown.</p> </tt> <table width="100%"><tr><td><br></td><td align=right> <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> </td></tr></table> <p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font> </body> </html>