Master Note for LogMiner (Doc ID 1264738.1)

Concepts/Definitions

Changes made to user data or to the database dictionary are recorded in the Oracle redo log files so that database recovery operations can be performed. LogMiner provides an easy-to-use relational interface to redo log files (or archive logs) providing audit and data analysis capabilities.

Key capabilities of this interface are

• Finding logical corruption
• Planning for transaction level recovery
• Assistance with tuning and capacity planning
• Auditing data manipulation

Other references:

Note 300395.1 Using LogMiner, How to determine the cause of lots of redo generation
Note 111886.1 How to Setup LogMiner
Note 456814.1 How to Reclaim Space Used by LogMiner Tables?

Diagnosing

This Master Note is not intended to be a complete diagnostic guide for LogMiner. However, a few tips and hints about investigating problems with LogMiner are covered here.

Note 174504.1 is a key resource for initial investigation into problems you are experiencing.
The LogMiner can load redo records within a single transaction (until a commit record is found) when using the COMMITED_DATA_ONLY.  Note 807080.1 discusses problems with this option in environments with very large transactions (few commits). This can exhaust memory and lead to memory errors.

There can also be special considerations needed when using "continuous mining" functionality. See articles like Note 763700.1 and Note 759186.1 for more details on using "continuous mining".

When experiencing errors with the DBMS_LOGMNR procedure, search the MyOracle Support KnowledgeBase using keywords DBMS_LOGMNR and the error message encountered.

Common Issues

Bug 9253557 addressed the problem with memory exhaustion when using COMMITTED_DATA_ONLY. This problem is patched on top of 10.2.0.4 and 11.2.0.1.

In 9.2.x and 10.1.x, there can be issues associated with adding and removing virtual columns for certain types of indexes. Bug 2894448 addresses this problem at 10.1.0.2 and on top of 9.2.0.8.

There can be character conversion issues with LogMiner when mining the redo/undo information on a different database with a different characterset defined than on the source database. Bug 8753157 addresses this problem and a patch is available at 10.2.0.5.

Additional Resources

Communities: Database Utilities
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