dump日志文件的内容的研究

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本文介绍如何dump online的日志文件头部信息（也包括归档）
PURPOSE This article explain how to obtain a dump of the header information in the online redo log file(s), as well as obtaining selected information from the online or archived redo log files.

SCOPE & APPLICATION Informational

You are working with Oracle Technical Support. As part of the diagnostic process, you have been asked to take a dump of the redo log files. The information in the logs is often used to help diagnose corruption issues. （在一些诊断时，需要dump redo log file）

The following commands will be used in this process:
1. The 'alter session' command is used to dump redo headers.
2. Use the 'alter system dump logfile' to dump log file contents.
alter session用于dump 日志头而‘system dump logfile' 用于dump 日志内容。This command requires 'ALTER SYSTEM' system privilege（需要 'ALTER SYSTEM' 系统权限）. The database can be in mount, nomount or open state when the command is issued（可以是nomount状态）. An online log file or an archived log file can be dumped. It is even possible to dump a file from another database, as long as the operating systems are the same（只要操作系统一样，也可以dump其他数据库的dump文件）.

Output from the command is put into the session's trace file.

The following ways of dumping a redo log file are covered:

1. To dump records based in DBA (Data Block Address) --基于dba
2. To dump records based on RBA (Redo Block Address) --基于rda
3. To dump records based on time --基于时间
4. To dump records based on layer and opcode --基于？？
5. Dump the file header information --dump头部信息
6. Dump an entire log file: --dump全部日志文件
1. To dump records based on DBA (Data Block Address) --基于dba
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This will dump all redo records for the range of data blocks specified for a given file # and block # range. 指定文件号和block范围即可。From sqldba or svrmgr, issue the following command:

ALTER SYSTEM DUMP LOGFILE 'filename'
DBA MIN fileno . blockno
DBA MAX fileno . blockno;
Example:
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ALTER SYSTEM DUMP LOGFILE 'u01/oracle/V7323/dbs/arch1_76.dbf'
DBA MIN 5 . 31125
DBA MAX 5 . 31150;

This will cause all the changes to the specified range of data blocks to be dumped to the trace file. In the example given, all redo records for file #5, blocks 31125 thru 31150 are dumped.

2. To dump records based on RBA (Redo Block Address)
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This will dump all redo records for the range of redo addresses specified for the given sequence number and block number.
指定scn号和块number
Syntax:
ALTER SYSTEM DUMP LOGFILE 'filename'
RBA MIN seqno . blockno
RBA MAX seqno . blockno;
Example:
ALTER SYSTEM DUMP LOGFILE 'u01/oracle/V7323/dbs/arch1_76.dbf'
RBA MIN 2050 . 13255
RBA MAX 2255 . 15555;

3. To dump records based on time.
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Using this option will cause redo records created within the time range specified to be dumped to the trace file.
指定时间范围。From sqldba or svrmgr, issue the following command:
ALTER SYSTEM DUMP LOGFILE 'filename'
TIME MIN value
TIME MAX value;

Example:
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ALTER SYSTEM DUMP LOGFILE 'u01/oracle/V7323/dbs/arch1_76.dbf'
TIME MIN 299425687
TIME MAX 299458800;
Please Note: the time value is given in REDO DUMP TIME

4. To dump records based on layer and opcode.
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LAYER and OPCODE are used to dump all log records for a particular type of redo record, such as all dropped row pieces.
From sqldba or svrmgr, issue the following command:
用于dump特定重做记录的所有日志记录。比如由sysdba执行的所有删掉的行 layer，与opcode应该是oracle自身的代码了。
ALTER SYSTEM DUMP LOGFILE 'filename'
LAYER value
OPCODE value;
Example:
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ALTER SYSTEM DUMP LOGFILE 'u01/oracle/V7323/dbs/arch1_76.dbf'
LAYER 11
OPCODE 3;

5. Dump the file header information:dump online的头部信息。
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This will dump file header information for every online redo log file. From sqldba or svrmgr, issue the following command:
alter session set events 'immediate trace name redohdr level 10';

6. Dump an entire log file:指定log的路径即可，可以是其他的数据库的
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From sqldba or svrmgr, issue the following command:
ALTER SYSTEM DUMP LOGFILE 'filename';
Please note:
Fully qualify the filename, and include the single quotes.

Example:
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ALTER SYSTEM DUMP LOGFILE 'u01/oracle/V7323/dbs/arch1_76.dbf'