ORACLE checkpoint cnt和checkpoint scn

刚才上网搜checkpoint cnt，看到EYGLE写的一篇文章，写得不错，存起来方便以后学习。
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通过试验说明checkpoint cnt 和checkpoint scn的关系
1.在不同条件下转储控制文件
 
SQL> alter session set events 'immediate trace name CONTROLF level 10';
Session altered.
SQL> alter tablespace system begin backup;
Tablespace altered.
SQL> alter session set events 'immediate trace name CONTROLF level 10';
Session altered.
SQL> alter system checkpoint;
System altered.
SQL> alter session set events 'immediate trace name CONTROLF level 10'
2 /
Session altered.
SQL> alter tablespace system end backup;
Tablespace altered.
SQL> alter session set events 'immediate trace name CONTROLF level 10';
Session altered.
 
notes:
alter session set events 'immediate trace name CONTROLF level 10';
用于转储控制文件.
 
2.获得以下跟踪文件信息(仅研究system表空间记录,请注意红色部分):
a.正常情况下转储控制文件
 
***************************************************************************
DATA FILE RECORDS
***************************************************************************
(blkno = 0x6, size = 180, max = 100, in-use = 24, last-recid= 574)
DATA FILE #1:
(name #4) /opt/oracle/oradata/hsjf/system01.dbf
creation size=32000 block size=8192 status=0xe head=4 tail=4 dup=1
tablespace 0, index=1 krfil=1 prev_file=0
unrecoverable scn: 0x0000.00000000 04/23/2004 01:20:52
Checkpoint cnt:1567 scn: 0x0000.0148181c 06/22/2004 18:58:46
Stop scn: 0xffff.ffffffff 06/22/2004 18:58:05
Creation Checkpointed at scn: 0x0000.000000ae 07/16/2003 03:40:10
thread:1 rba:(0x1.3.10)
enabled threads: 01000000 00000000 00000000 00000000 00000000 00000000
00000000 00000000
Offline scn: 0x0000.013b46fd prev_range: 0
Online Checkpointed at scn: 0x0000.013b46fe 05/28/2004 23:37:17
thread:1 rba:(0x1.2.0)
enabled threads: 01000000 00000000 00000000 00000000 00000000 00000000
00000000 000