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Java > Open Source Codes > com > db4o > ext > SystemInfo


1 /* Copyright (C) 2004 - 2006 db4objects Inc. http://www.db4o.com
2
3 This file is part of the db4o open source object database.
4
5 db4o is free software; you can redistribute it and/or modify it under
6 the terms of version 2 of the GNU General Public License as published
7 by the Free Software Foundation and as clarified by db4objects' GPL
8 interpretation policy, available at
9 http://www.db4o.com/about/company/legalpolicies/gplinterpretation/
10 Alternatively you can write to db4objects, Inc., 1900 S Norfolk Street,
11 Suite 350, San Mateo, CA 94403, USA.
12
13 db4o is distributed in the hope that it will be useful, but WITHOUT ANY
14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
16 for more details.
17
18 You should have received a copy of the GNU General Public License along
19 with this program; if not, write to the Free Software Foundation, Inc.,
20 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
21 package com.db4o.ext;
22
23
24 /**
25  * provides information about system state and system settings.
26  */
27 public interface SystemInfo {
28     
29     /**
30      * returns the number of entries in the Freespace Manager.
31      * <br><br>A high value for the number of freespace entries
32      * is an indication that the database is fragmented and
33      * that defragment should be run.
34      * @return the number of entries in the Freespace Manager.
35      */
36     public int freespaceEntryCount();
37     
38     /**
39      * returns the freespace size in the database in bytes.
40      * <br><br>When db4o stores modified objects, it allocates
41      * a new slot for it. During commit the old slot is freed.
42      * Free slots are collected in the freespace manager, so
43      * they can be reused for other objects.
44      * <br><br>This method returns a sum of the size of all
45      * free slots in the database file.
46      * <br><br>To reclaim freespace run defragment.
47      * @return the freespace size in the database in bytes.
48      */
49     public long freespaceSize();
50
51     /**
52      * Returns the total size of the database on disk.
53      * @return total size of database on disk
54      */
55     public long totalSize();
56
57 }
58
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