154 lines
8.4 KiB
HTML
154 lines
8.4 KiB
HTML
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<meta name="DC.Title" content="Commitment control" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 2006" />
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<title>Commitment control</title>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Commitment control</h1>
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<div><p></p>
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<div class="section"><p>Through commitment control, your Java™ program has another level of control
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over changing a file. With commitment control turned on, transactions to a
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file are pending until they are either committed or rolled back. If committed,
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all changes are put to the file. If rolled back, all changes are discarded.
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The transaction can be changing an existing record, adding a record, deleting
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a record, or even reading a record depending on the commitment control lock
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level specified on the open().</p>
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</div>
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<div class="section"><p>The levels of commitment control are as follows:</p>
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</div>
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<div class="section"><ul><li><a href="javadoc/com/ibm/as400/access/AS400File.html#COMMIT_LOCK_LEVEL_ALL"> All</a> - Every record accessed in the file is locked until
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the transaction is committed or rolled back.</li>
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<li><a href="javadoc/com/ibm/as400/access/AS400File.html#COMMIT_LOCK_LEVEL_CHANGE"> Change</a> - Updated, added, and deleted records in the
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file are locked until the transaction is committed or rolled back.</li>
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<li><a href="javadoc/com/ibm/as400/access/AS400File.html#COMMIT_LOCK_LEVEL_CURSOR_STABILITY"> Cursor Stability</a> - Updated, added, and deleted records
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in the file are locked until the transaction is committed or rolled back.
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Records that are accessed but not changed are locked only until another record
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is accessed.</li>
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<li><a href="javadoc/com/ibm/as400/access/AS400File.html#COMMIT_LOCK_LEVEL_NONE"> None</a> - There is no commitment control on the file. Changes
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are immediately put to the file and cannot be rolled back.</li>
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</ul>
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</div>
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<div class="section"><p>You can use the <a href="javadoc/com/ibm/as400/access/AS400File.html#STARTCOMMITMENTCONTROL(INT)"> startCommitmentControl()</a> method to start commitment
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control. Commitment control applies to the AS400 <strong>connection</strong>. Once commitment
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control is started for a connection, it applies to all files opened under
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that connection from the time that commitment control was started. Files opened
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before commitment control is started are not under commitment control. The
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level of commitment control for individual files is specified on the <a href="javadoc/com/ibm/as400/access/AS400File.html#OPEN()">open()</a> method.
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Specify <a href="javadoc/com/ibm/as400/access/AS400File.html#COMMIT_LOCK_LEVEL_DEFAULT"> COMMIT_LOCK_LEVEL_DEFAULT</a> to use the same level of commitment
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control as was specified on the startCommitmentControl() method.</p>
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</div>
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<div class="section"><p>For example:</p>
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</div>
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<div class="section"><div class="p"><pre> // Create an AS400 object, the files exist on this
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// server.
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AS400 sys = new AS400("mySystem.myCompany.com");
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// Create three file objects
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SequentialFile myFile = new SequentialFile(sys, "/QSYS.LIB/MYLIB.LIB/MYFILE.FILE/%FILE%.MBR");
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SequentialFile yourFile = new SequentialFile(sys, "/QSYS.LIB/YOURLIB.LIB/YOURFILE.FILE/%FILE%.MBR");
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SequentialFile ourFile = new SequentialFile(sys, "/QSYS.LIB/OURLIB.LIB/OURFILE.FILE/%FILE%.MBR");
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// Open yourFile before starting commitment control
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// No commitment control applies to this file. The
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// commit lock level parameter is ignored because
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// commitment control is not started for the connection.
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yourFile.setRecordFormat(new YOURFILEFormat());
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yourFile.open(AS400File.READ_WRITE, 0, AS400File.COMMIT_LOCK_LEVEL_DEFAULT);
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// Start commitment control for the connection.
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// Note: Any of the three files might be used for
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// this call to startCommitmentControl().
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myFile.startCommitmentControl(AS400File.COMMIT_LOCK_LEVEL_CHANGE);
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// Open myFile and ourFile
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myFile.setRecordFormat(new MYFILEFormat());
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// Use the same commit lock level as specified
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// when commitment control was started
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myFile.open(AS400File.WRITE_ONLY, 0, COMMIT_LOCK_LEVEL_DEFAULT);
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ourFile.setRecordFormat(new OURFILEFormat());
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// Specify a different commit lock level than
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// when commitment control was started
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ourFile.open(AS400File.READ_WRITE, 0, COMMIT_LOCK_LEVEL_CURSOR_STABILITY);
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// write and update records in all three files
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....
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// Commit the changes for files myFile and ourFile.
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// Note that the commit commits all changes for the connection
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// even though it is invoked on only one AS400File object.
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myFile.commit();
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// Close the files
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myFile.close();
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yourFile.close();
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ourFile.close();
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// End commitment control
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// This ends commitment control for the connection.
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ourFile.endCommitmentControl();
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// Disconnect since I am done using record-level access
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sys.disconnectService(AS400.RECORDACCESS);</pre>
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</div>
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</div>
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<div class="section"><p>The <a href="javadoc/com/ibm/as400/access/AS400File.html#COMMIT()">commit()</a> method commits all transactions since the last
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commit boundary for the <strong>connection</strong>. The <a href="javadoc/com/ibm/as400/access/AS400File.html#ROLLBACK()"> rollback()</a> method discards all transactions since the
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last commit boundary for the <strong>connection</strong>. Commitment control for a connection
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is ended through the <a href="javadoc/com/ibm/as400/access/AS400File.html#ENDCOMMITMENTCONTROL()"> endCommitmentControl()</a> method. If a file is closed before
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invoking the commit() or rollback() method, all uncommitted transactions are
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rolled back. All files opened under commitment control must be closed before
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the endCommitmentControl() method is called.</p>
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</div>
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<div class="section"><p>The following examples shows how to start commitment control,
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commit or roll back functions, and then end commitment control:</p>
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</div>
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<div class="section"><div class="p"><pre> // ... assume the AS400 object and file have been
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// instantiated.
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// Start commitment control for *CHANGE
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aFile.startCommitmentControl(AS400File.COMMIT_LOCK_LEVEL_CHANGE);
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// ... open the file and do several changes. For
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// example, update, add or delete records.
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// Based on a flag either save or discard the
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// transactions.
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if (saveChanges)
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aFile.commit();
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else
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aFile.rollback();
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// Close the file
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aFile.close();
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// End commitment control for the connection.
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aFile.endCommitmentControl();</pre>
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</div>
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</div>
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</div>
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</body>
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