Databases Reference
In-Depth Information
Log Miner
Oracle Log Miner is another tool the DBA can use to view past activity in the data-
base. The Log Miner tool can help the DBA find changed records in redo log files
by using a set of PL/SQL procedures and functions. Log Miner extracts all DDL
and DML activity from the redo log files for viewing by a DBA via the dynamic
performance view V$LOGMNR_CONTENTS. In addition to extracting the DDL and
DML statements used to change the database, the V$LOGMNR_CONTENTS view also
contains the DML or DDL statements needed to reverse the change made to the
database. This is a good tool for not only pinpointing when changes were made to
a table but also for automatically generating the SQL statements needed to reverse
those changes.
Log Miner works differently from Oracle's flashback query feature. The flash-
back query feature allows a user to see the contents of a table at a specified time
in the past; Log Miner can search a time period for all DDL against the table. A
flashback query uses the undo information stored in the undo tablespace; Log
Miner uses redo logs. Both of these tools can be useful for tracking down how and
when changes to database objects took place.
Log Miner may be configured and used either from a SQL command line or
via a GUI-based interface within Oracle Enterprise Manager (OEM), as shown
here, by selecting Tools
Database Applications
Logminer Viewer.
