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<h2 class="title" style="clear: both"><a id="autocommit"></a>Auto Commit</h2>
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<p>
While transactions are frequently used to provide atomicity to
multiple database
<span>
or store
</span>
operations, it is sometimes necessary to perform
a single database
<span>
or store
</span>
operation under the control of a transaction.
Rather than force you to obtain a transaction, perform the single
write operation, and then either commit or abort the transaction,
you can automatically group this sequence of events using
<span class="emphasis"><em>auto commit</em></span>.
</p>
<p>
To use auto commit:
</p>
<div class="orderedlist">
<ol type="1">
<li>
<p>
Open your environment and your databases
<span>
or store
</span>
so that they support
transactions. See <a class="xref" href="enabletxn.html" title="Chapter 2. Enabling Transactions">Enabling Transactions</a>
for details.
</p>
</li>
<li>
<p>
Do not provide a transactional handle to the method that is
performing the database
<span>
or store
</span>
write operation.
</p>
</li>
</ol>
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<p>
Note that auto commit is not available for cursors. You must always
open your cursor using a transaction if you want the cursor's
operations to be transactional protected. See
<a class="xref" href="txncursor.html" title="Transactional Cursors">Transactional Cursors</a> for details on using
transactional cursors.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Note</h3>
<p>
Never have more than one active transaction in your thread
at a time. This is especially a problem if you mix an
explicit transaction with another operation that uses auto
commit. Doing so can result in undetectable deadlocks.
</p>
</div>
<p>
For example, the following uses auto commit to perform the database write operation:
</p>
<pre class="programlisting">package db.txn;
import com.sleepycat.db.Database;
import com.sleepycat.db.DatabaseConfig;
import com.sleepycat.db.DatabaseEntry;
import com.sleepycat.db.DatabaseException;
import com.sleepycat.db.Environment;
import com.sleepycat.db.EnvironmentConfig;
import java.io.File;
...
Database myDatabase = null;
Environment myEnv = null;
try {
EnvironmentConfig myEnvConfig = new EnvironmentConfig();
myEnvConfig.setInitializeCache(true);
myEnvConfig.setInitializeLocking(true);
myEnvConfig.setInitializeLogging(true);
myEnvConfig.setTransactional(true);
myEnv = new Environment(new File("/my/env/home"),
myEnvConfig);
// Open the database.
DatabaseConfig dbConfig = new DatabaseConfig();
dbConfig.setTransactional(true);
dbConfig.setType(DatabaseType.BTREE);
myDatabase = myEnv.openDatabase(null, // txn handle
"sampleDatabase", // db file name
null, // db name
dbConfig);
String keyString = "thekey";
String dataString = "thedata";
DatabaseEntry key =
new DatabaseEntry(keyString.getBytes("UTF-8"));
DatabaseEntry data =
new DatabaseEntry(dataString.getBytes("UTF-8"));
// Perform the write. Because the database was opened to
// support transactions, this write is performed using auto commit.
myDatabase.put(null, key, data);
} catch (DatabaseException de) {
// Exception handling goes here
} </pre>
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