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comparison src/org/dancres/blitz/txn/UnsyncdOps.java @ 0:3dc0c5604566

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Initial checkin of blitz 2.0 fcs - no installer yet.
author Dan Creswell <dan.creswell@gmail.com>
date Sat, 21 Mar 2009 11:00:06 +0000
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1 package org.dancres.blitz.txn;
2
3 import org.dancres.blitz.BootInfo;
4
5 /**
6 <p>UnsyncdOps provides boot-time information concerning the maximum number
7 of log operations which might have occurred since the last full
8 checkpoint/sync was initiated.</p>
9
10 <p>We deliberately return double the op count to allow for interrupted
11 checkpoints. An interrupted checkpoint leads to two contiguous
12 log files with no separating checkpoint image. The maximum number
13 of operations before the next checkpoint would, therefore be
14 double the maximum number of ops per checkpoint. A checkpoint can
15 only be interrupted as the result of violent shutdown and, restart
16 will immediately resolve state using the UnsyncdOps. If restart
17 fails to complete, there will be no further log entries or
18 checkpoints and the next restart will, worst case, apply the
19 state resolution twice which isn't harmful.</p>
20 */
21 public class UnsyncdOps implements BootInfo, java.io.Serializable {
22 private int theOpCount;
23
24 UnsyncdOps(int anOpCount) {
25 theOpCount = 2 * anOpCount;
26 }
27
28 public int getOpsSinceLastCheckpoint() {
29 return theOpCount;
30 }
31 }