前几天说过，Oracle10g Events CONTROLF的改变，当时猜测控制文件的变化可能是为了满足Oracle10g Grid运算支持大量并行实例的需要。
单实例节点控制文件转储包含的位图如下:
Database checkpoint: Thread=1 scn: 0x0000.0007276a
Threads: #Enabled=1, #Open=1, Head=1, Tail=1
enabled threads: 01000000 00000000 00000000 00000000 00000000 00000000
00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
今天转储了一个RAC数据库的控制文件，验证了这个猜测：
***************************************************************************
DATABASE ENTRY
***************************************************************************
(size = 316, compat size = 316, section max = 1, section in-use = 1,
last-recid= 0, old-recno = 0, last-recno = 0)
(extent = 1, blkno = 1, numrecs = 1)
12/27/2006 16:25:27
DB Name "EYGLE"
Database flags = 0x00404000 0x00001000
Controlfile Creation Timestamp 12/27/2006 16:25:30
Incmplt recovery scn: 0x0000.00000000
Resetlogs scn: 0x0000.00000001 Resetlogs Timestamp 12/27/2006 16:25:27
Prior resetlogs scn: 0x0000.00000000 Prior resetlogs Timestamp 01/01/1988 00:00:00
Redo Version: compatible=0xa200100
#Data files = 5, #Online files = 5
Database checkpoint: Thread=2 scn: 0x0000.008a8531
Threads: #Enabled=2, #Open=2, Head=2, Tail=1
enabled threads: 01100000 00000000 00000000 00000000 00000000 00000000
00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
Oracle不断的将位图引入数据库的各个治理单元，显然旨在性能提高。
-The End-
http://www.eygle.com/archives/2007/02/controlfile_bitmap.Html
