关于数据文件头内容与oracle启动

来源：互联网发布：辨析题存在就是被告知编辑：程序博客网时间：2024/05/29 12:18

可以通过一个内部事件来转储数据文件头信息，这个常用的命令是：

alter session set events 'immediate trace namefile_hdrs level 10';

那么我们来看一下这个命令得到的trace文件及内容。
immediate关闭数据库，在mount状态下执行该命令:

SQL> startup mount;
ORACLE instance started.

Total System Global Area 139531744 bytes
FixedSize                  452064 bytes
VariableSize            121634816 bytes
DatabaseBuffers          16777216 bytes
RedoBuffers                667648 bytes
Database mounted.
SQL> alter session set events 'immediate trace namefile_hdrs level 10';

Session altered.

选取一个文件的信息,这里选择myoracle01.dbf文件，我们注意，以下就是trace文件摘录的信息:

DATA FILE #4:
(name #4)/opt/oracle/oradata/myoracle/myoracle01.dbf
creation size=0 block size=8192 status=0xe head=4 tail=4dup=1
tablespace 4, index=4 krfil=4 prev_file=0
unrecoverable scn: 0x0000.00000000 01/01/198800:00:00
Checkpoint cnt:53 scn: 0x0000.002ac5f9 08/10/2006 20:58:21
Stop scn: 0x0000.002ac5f9 08/10/200620:58:21
Creation Checkpointed at scn: 0x0000.0015078d 06/06/2006 09:41:54
thread:0 rba:(0x0.0.0)
enabled threads: 00000000 00000000 00000000 0000000000000000 00000000
00000000 00000000
Offline scn: 0x0000.00000000 prev_range: 0
Online Checkpointed at scn: 0x0000.00000000
thread:0 rba:(0x0.0.0)
enabled threads: 00000000 00000000 00000000 0000000000000000 00000000
00000000 00000000
Hot Backup end marker scn: 0x0000.00000000
aux_file is NOT DEFINED
FILE HEADER:
       Software vsn=153092096=0x9200000, CompatibilityVsn=134217728=0x8000000
       Db ID=1407686520=0x53e79778, Db Name='MYORACLE'
       Activation ID=0=0x0
       Control Seq=973=0x3cd, File size=1280=0x500
       File Number=4, Blksiz=8192, File Type=3 DATA
Tablespace #4 - MYORACLE rel_fn:4
Creation  at   scn: 0x0000.0015078d06/06/2006 09:41:54
Backup taken at scn: 0x0000.00000000 01/01/1988 00:00:00thread:0
reset logs count:0x232bee1f scn: 0x0000.0007c781recovered at 08/10/2006 20:57:53
status:0x0 root dba:0x00000000 chkpt cnt: 53 ctlcnt:52
begin-hot-backup file size: 0
Checkpointed at scn: 0x0000.002ac5f9 08/10/200620:58:21
thread:1 rba:(0x35.1275.10)
enabled threads: 01000000 00000000 00000000 0000000000000000 00000000
00000000 00000000
Backup Checkpointed at scn: 0x0000.00000000
thread:0 rba:(0x0.0.0)
enabled threads: 00000000 00000000 00000000 0000000000000000 00000000
00000000 00000000
External cache id: 0x0 0x0 0x0 0x0
Absolute fuzzy scn: 0x0000.00000000
Recovery fuzzy scn: 0x0000.00000000 08/10/2006 10:46:03
Terminal Recovery Stamp scn: 0x0000.00000000 01/01/198800:00:00

注意，这其中"FILEHEADER"开始的信息就是来自数据文件头，之前的相关内容来自控制文件。

我们可以在mount状态下将myoracle01.dbf文件移除:

[oracle@jumper myoracle]$ mv myoracle01.dbfmyoracle01.dbf.n
[oracle@jumper myoracle]$ sqlplus "/ as sysdba"

SQL*Plus: Release 9.2.0.4.0 - Production on ThuAug 10 21:44:10 2006

Connected to:
Oracle9i Enterprise Edition Release 9.2.0.4.0 - Production
With the Partitioning option
JServer Release 9.2.0.4.0 - Production

SQL> alter session set events'immediate trace name file_hdrs level 10';

Session altered.

SQL> !

则"FILEHEADER"部分信息将无法获得。

此时报出的错误是，文件无法找到，也就是说当我们执行tracefile_hdrs时需要读取数据文件头，获得相关信息。

0 0