Introduction:
=============
LogMiner runs in an Oracle instance with the database either mounted or
unmounted. LogMiner uses a dictionary file, which is a special file that
indicates the database that created it as well as the time the file was
created. The dictionary file is not required, but is recommended. Without a
dictionary file, the equivalent SQL statements will use Oracle internal object
IDs for the object name and present column values as hex data.
For example, instead of the SQL statement:
INSERT INTO emp(name, salary) VALUES ('John Doe', 50000);
LogMiner will display:
insert into Object#2581(col#1, col#2) values (hextoraw('4a6f686e20446f65'),
hextoraw('c306'));"
Create a dictionary file by mounting a database and then extracting dictionary
information into an external file.
You must create the dictionary file from the same database that generated the
log files you want to analyze. Once created, you can use the dictionary file
to analyze redo logs.
When creating the dictionary, specify the following:
* DICTIONARY_FILENAME to name the dictionary file.
* DICTIONARY_LOCATION to specify the location of the file.
LogMiner analyzes redo log files from any version 8.0.x and later Oracle
database that uses the same database characterset and is running on the same
hardware as the analyzing instance.
Note: The LogMiner packages are owned by the SYS schema. Therefore, if you
are not connected as user SYS, you must include SYS in your call. For
example:
EXECUTE SYS.DBMS_LOGMNR_D.BUILD
To Create a Dictionary on the Oracle Database (9i and later)
====================================================
In the 9i and later releases, the ability to extract the dictionary to a flat file as well as creating a dictionary with the redo logs is available.
For example, enter the following to create the file dictionary.ora in /oracle/database:
1. Make sure to specify an existing directory that Oracle has permissions
to write to by the PL/SQL procedure by setting the initialization
parameter UTL_FILE_DIR in the init.ora.
For example, set the following to use /oracle/logs:
UTL_FILE_DIR =/oracle/database
Be sure to shutdown and restart the instance after adding UTL_FILE_DIR to the init or spfile.
If you do not reference this parameter, the procedure will fail.
2. Use SQL*Plus to mount and then open the database whose files you want to
analyze. For example, enter:
STARTUP
3. Execute the PL/SQL procedure DBMS_LOGMNR_D.BUILD. Specify both a file name
for the dictionary and a directory pathname for the file. This procedure
creates the dictionary file, which you should use to analyze log files.
For example, enter the following to create file dictionary.ora in
'/oracle/database/:
Example:
-------------
SQL> EXECUTE DBMS_LOGMNR_D.BUILD('dictionary.ora', -
2 '/oracle/database/', -
3 OPTIONS => DBMS_LOGMNR_D.STORE_IN_FLAT_FILE);
If extracting the database dictionary information to the redo logs, use the DBMS_LOGMNR_D.BUILD procedure with the STORE_IN_REDO_FILES option and do not specify a filename or location.
Example:
-------------
SQL> EXECUTE DBMS_LOGMNR_D.BUILD ( -
2 OPTIONS=>DBMS_LOGMNR_D.STORE_IN_REDO_LOGS);
Please note that to extract a dictionary to the redo logs, the database must be open and in ARCHIVELOG mode and archiving must be enabled
Also to make sure that the redo logs contain information that will provide the most value to you, you should enable at least minimal supplemental logging.
SQL> ALTER DATABASE ADD SUPPLEMENTAL LOG DATA
Specifying Redo Logs for Analysis
=================================
Once you have created a dictionary file, you can begin analyzing redo logs.
Your first step is to specify the log files that you want to analyze using
the ADD_LOGFILE procedure. Use the following constants:
* NEW to create a new list.
* ADDFILE to add redo logs to a list.
* REMOVEFILE to remove redo logs from the list.
To Use LogMiner:
1. Use SQL*Plus to start an Oracle instance, with the database either mounted
or unmounted.
For example, enter:
STARTUP
2. Create a list of logs by specifying the NEW option when executing the
DBMS_LOGMNR.ADD_LOGFILE procedure. For example, enter the following to
specify /oracle/logs/log1.f:
(INCLUDE THE '-' WHEN ENTERING THE FOLLOWING)
EXECUTE DBMS_LOGMNR.ADD_LOGFILE( -
LOGFILENAME => '/oracle/logs/log1.f', -
OPTIONS => dbms_logmnr.NEW);
3. If desired, add more logs by specifying the ADDFILE option.
For example, enter the following to add /oracle/logs/log2.f:
(INCLUDE THE '-' WHEN ENTERING THE FOLLOWING)
EXECUTE DBMS_LOGMNR.ADD_LOGFILE( -
LOGFILENAME => '/oracle/logs/log2.f', -
OPTIONS => dbms_logmnr.ADDFILE);
4. If desired, remove logs by specifying the REMOVEFILE option.
For example, enter the following to remove /oracle/logs/log2.f:
(INCLUDE THE '-' WHEN ENTERING THE FOLLOWING)
EXECUTE DBMS_LOGMNR.ADD_LOGFILE( -
LOGFILENAME => '/oracle/logs/log2.f', -
OPTIONS => dbms_logmnr.REMOVEFILE);
Using LogMiner:
===============
Once you have created a dictionary file and specified which logs to analyze,
you can start LogMiner and begin your analysis. Use the following options to
narrow the range of your search at start time:
This option Specifies
=========== =========
STARTSCN The beginning of an SCN range.
ENDSCN The termination of an SCN range.
STARTTIME The beginning of a time interval.
ENDTIME The end of a time interval.
DICTFILENAME The name of the dictionary file.
Once you have started LogMiner, you can make use of the following data
dictionary views for analysis:
This view Displays information about
=================== ==================================================
V$LOGMNR_DICTIONARY The dictionary file in use.
V$LOGMNR_PARAMETERS Current parameter settings for LogMiner.
V$LOGMNR_LOGS Which redo log files are being analyzed.
V$LOGMNR_CONTENTS The contents of the redo log files being analyzed.
To Use LogMiner:
================
1. Issue the DBMS_LOGMNR.START_LOGMNR procedure to start LogMiner utility.
For example, to start LogMiner using /oracle/dictionary.ora, issue:
(INCLUDE THE '-' WHEN ENTERING THE FOLLOWING)
EXECUTE DBMS_LOGMNR.START_LOGMNR( -
DICTFILENAME =>'/oracle/dictionary.ora');
Optionally, set the STARTTIME and ENDTIME parameters to filter data by time.
Note that the procedure expects date values: use the TO_DATE function to
specify date and time, as in this example:
(INCLUDE THE '-' WHEN ENTERING THE FOLLOWING)
EXECUTE DBMS_LOGMNR.START_LOGMNR( -
DICTFILENAME => '/oracle/dictionary.ora', -
STARTTIME => to_date('01-Jan-1998 08:30:00', 'DD-MON-YYYY HH:MI:SS'), -
ENDTIME => to_date('01-Jan-1998 08:45:00', 'DD-MON-YYYY HH:MI:SS'));
Use the STARTSCN and ENDSCN parameters to filter data by SCN, as in this
example:
(INCLUDE THE '-' WHEN ENTERING THE FOLLOWING)
EXECUTE DBMS_LOGMNR.START_LOGMNR( -
DICTFILENAME => '/oracle/dictionary.ora', -
STARTSCN => 100, -
ENDSCN => 150);
2. View the output via the V$LOGMNR_CONTENTS table. LogMiner returns all rows
in SCN order, which is the same order applied in media recovery.
For example,the following query lists information about operations:
SELECT operation, sql_redo FROM v$logmnr_contents;
OPERATION SQL_REDO
--------- ----------------------------------------------------------
INTERNAL
INTERNAL
START set transaction read write;
UPDATE update SYS.UNDO$ set NAME = 'RS0', USER# = 1, FILE# = 1, BLOCK# = 2450, SCNBAS =
COMMIT commit;
START set transaction read write;
UPDATE update SYS.UNDO$ set NAME = 'RS0', USER# = 1, FILE# = 1, BLOCK# = 2450, SCNBAS =
COMMIT commit;
START set transaction read write;
UPDATE update SYS.UNDO$ set NAME = 'RS0', USER# = 1, FILE# = 1, BLOCK# = 2450, SCNBAS =
COMMIT commit;
11 rows selected.
Analyzing Archived Redo Log Files from Other Databases:
=======================================================
You can run LogMiner on an instance of a database while analyzing redo log
files from a different database. To analyze archived redo log files from other
databases,
LogMiner must:
* Access a dictionary file that is both created from the same database as the
redo log files and created with the same database character set.
* Run on the same hardware platform that generated the log files, although it
does not need to be on the same system.
* Use redo log files that can be applied for recovery from Oracle version 8.0
and later.
