Import BSDDB 4.7.25 (as of svn r89086)
This commit is contained in:
Zachary Ware
135
docs/api_cxx/txn_begin.html
Normal file
135
docs/api_cxx/txn_begin.html
Normal file
@@ -0,0 +1,135 @@
|
||||
<!--$Id: txn_begin.html 63573 2008-05-23 21:43:21Z trent.nelson $-->
|
||||
<!--Copyright (c) 1997,2008 Oracle. All rights reserved.-->
|
||||
<!--See the file LICENSE for redistribution information.-->
|
||||
<html>
|
||||
<head>
|
||||
<title>Berkeley DB: DbEnv::txn_begin</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>DbEnv::txn_begin</b>
|
||||
</td>
|
||||
<td align=right>
|
||||
<a href="../api_cxx/api_core.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>
|
||||
#include <db_cxx.h>
|
||||
<p>
|
||||
int
|
||||
DbEnv::txn_begin(DbTxn *parent, DbTxn **tid, u_int32_t flags);
|
||||
</pre></b>
|
||||
<hr size=1 noshade>
|
||||
<b>Description: DbEnv::txn_begin</b>
|
||||
<p>The DbEnv::txn_begin method creates a new transaction in the environment
|
||||
and copies a pointer to a <a href="../api_cxx/txn_class.html">DbTxn</a> that uniquely identifies it into
|
||||
the memory to which <b>tid</b> refers. Calling the <a href="../api_cxx/txn_abort.html">DbTxn::abort</a>,
|
||||
<a href="../api_cxx/txn_commit.html">DbTxn::commit</a> or <a href="../api_cxx/txn_discard.html">DbTxn::discard</a> methods will discard the returned
|
||||
handle.</p>
|
||||
<p><b>Note: Transactions may only span threads if they do so serially;
|
||||
that is, each transaction must be active in only a single thread
|
||||
of control at a time. This restriction holds for parents of nested
|
||||
transactions as well; no two children may be concurrently active in
|
||||
more than one thread of control at any one time.</b></p>
|
||||
<p><b>Note: Cursors may not span transactions; that is, each cursor must be
|
||||
opened and closed within a single transaction.</b></p>
|
||||
<p><b>Note: A parent transaction may not issue any Berkeley DB operations -- except for
|
||||
DbEnv::txn_begin, <a href="../api_cxx/txn_abort.html">DbTxn::abort</a> and <a href="../api_cxx/txn_commit.html">DbTxn::commit</a> -- while it has
|
||||
active child transactions (child transactions that have not yet been
|
||||
committed or aborted).</b></p>
|
||||
<p>The DbEnv::txn_begin method
|
||||
either returns a non-zero error value
|
||||
or throws an exception that encapsulates a non-zero error value on
|
||||
failure, and returns 0 on success.
|
||||
</p>
|
||||
<b>Parameters</b> <br>
|
||||
<b>flags</b><ul compact><li>The <b>flags</b> parameter must be set to 0 or by bitwise inclusively <b>OR</b>'ing together one
|
||||
or more of the following values:
|
||||
<br>
|
||||
<b><a name="DB_READ_COMMITTED">DB_READ_COMMITTED</a></b><ul compact><li>This transaction will have degree 2 isolation. This provides for cursor
|
||||
stability but not repeatable reads. Data items which have been
|
||||
previously read by this transaction may be deleted or modified by other
|
||||
transactions before this transaction completes.</ul>
|
||||
<b><a name="DB_READ_UNCOMMITTED">DB_READ_UNCOMMITTED</a></b><ul compact><li>This transaction will have degree 1 isolation. Read operations
|
||||
performed by the transaction may read modified but not yet committed
|
||||
data. Silently ignored if the DB_READ_UNCOMMITTED flag was not
|
||||
specified when the underlying database was opened.</ul>
|
||||
<b><a name="DB_TXN_NOSYNC">DB_TXN_NOSYNC</a></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.
|
||||
<p>This behavior may be set for a Berkeley DB environment using the
|
||||
<a href="../api_cxx/env_set_flags.html">DbEnv::set_flags</a> method. Any value specified to this method overrides
|
||||
that setting.</p></ul>
|
||||
<b><a name="DB_TXN_NOWAIT">DB_TXN_NOWAIT</a></b><ul compact><li>If a lock is unavailable for any Berkeley DB operation performed in the context
|
||||
of this transaction, cause the operation to
|
||||
either return <a href="../ref/program/errorret.html#DB_LOCK_DEADLOCK">DB_LOCK_DEADLOCK</a> or throw a
|
||||
<a href="../api_cxx/deadlock_class.html">DbDeadlockException</a> exception (or return
|
||||
<a href="../ref/program/errorret.html#DB_LOCK_NOTGRANTED">DB_LOCK_NOTGRANTED</a> or throw a <a href="../api_cxx/lockng_class.html">DbLockNotGrantedException</a>
|
||||
exception if the database environment has been configured using the
|
||||
<a href="../api_cxx/env_set_flags.html#DB_TIME_NOTGRANTED">DB_TIME_NOTGRANTED</a> flag).
|
||||
<p>This behavior may be set for a Berkeley DB environment using the
|
||||
<a href="../api_cxx/env_set_flags.html">DbEnv::set_flags</a> method. Any value specified to this method overrides
|
||||
that setting.</p></ul>
|
||||
<b><a name="DB_TXN_SNAPSHOT">DB_TXN_SNAPSHOT</a></b><ul compact><li>This transaction will execute with <a href="../ref/transapp/read.html">snapshot isolation</a>. For databases with the <a href="../api_cxx/db_open.html#DB_MULTIVERSION">DB_MULTIVERSION</a>
|
||||
flag set, data values will be read as they are when the transaction
|
||||
begins, without taking read locks. Silently ignored for operations on
|
||||
databases with <a href="../api_cxx/db_open.html#DB_MULTIVERSION">DB_MULTIVERSION</a> not set on the underlying
|
||||
database (read locks are acquired).
|
||||
<p>The error <a name="DB_LOCK_DEADLOCK">DB_LOCK_DEADLOCK</a> will be returned from update
|
||||
operations if a snapshot transaction attempts to update data
|
||||
which was modified after the snapshot transaction read it.</p></ul>
|
||||
<b><a name="DB_TXN_SYNC">DB_TXN_SYNC</a></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
|
||||
DB_TXN_NOSYNC flag was specified to the
|
||||
<a href="../api_cxx/env_set_flags.html">DbEnv::set_flags</a> method. Any value specified to this method overrides
|
||||
that setting.</p></ul>
|
||||
<b><a name="DB_TXN_WAIT">DB_TXN_WAIT</a></b><ul compact><li>If a lock is unavailable for any Berkeley DB operation performed in the context
|
||||
of this transaction, wait for the lock.
|
||||
<p>This behavior is the default for Berkeley DB environments unless the
|
||||
DB_TXN_NOWAIT flag was specified to the
|
||||
<a href="../api_cxx/env_set_flags.html">DbEnv::set_flags</a> method. Any value specified to this method overrides
|
||||
that setting.</p></ul>
|
||||
<b><a name="DB_TXN_WRITE_NOSYNC">DB_TXN_WRITE_NOSYNC</a></b><ul compact><li>Write, but do not synchronously flush, the log when this transaction
|
||||
commits. 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 if the system fails, it is
|
||||
possible some number of the most recently committed transactions may be
|
||||
undone during recovery. The number of transactions at risk is governed
|
||||
by how often the system flushes dirty buffers to disk and how often the
|
||||
log is flushed or checkpointed.
|
||||
<p>This behavior may be set for a Berkeley DB environment using the
|
||||
<a href="../api_cxx/env_set_flags.html">DbEnv::set_flags</a> method. Any value specified to this method overrides
|
||||
that setting.</p></ul>
|
||||
<br></ul>
|
||||
<b>parent</b><ul compact><li>If the <b>parent</b> parameter is non-NULL, the new transaction will
|
||||
be a nested transaction, with the transaction indicated by
|
||||
<b>parent</b> as its parent. Transactions may be nested to any level.
|
||||
In the presence of distributed transactions and two-phase commit, only
|
||||
the parental transaction, that is a transaction without a <b>parent</b>
|
||||
specified, should be passed as an parameter to <a href="../api_cxx/txn_prepare.html">DbTxn::prepare</a>.</ul>
|
||||
<br>
|
||||
<br><b>Errors</b>
|
||||
<p>If the maximum number of concurrent transactions has been reached, the DbEnv::txn_begin method will fail and
|
||||
either return ENOMEM or
|
||||
throw a DbMemoryException.</p>
|
||||
<hr size=1 noshade>
|
||||
<br><b>Class</b>
|
||||
<a href="../api_cxx/env_class.html">DbEnv</a>, <a href="../api_cxx/txn_class.html">DbTxn</a>
|
||||
<br><b>See Also</b>
|
||||
<a href="../api_cxx/txn_list.html">Transaction Subsystem and Related Methods</a>
|
||||
</tt>
|
||||
<table width="100%"><tr><td><br></td><td align=right>
|
||||
<a href="../api_cxx/api_core.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>
|
||||
Reference in New Issue
Block a user