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Don Burleson Blog 







enable_ddl_logging Tips

Oracle Database Tips by Donald BurlesonFebruary 6, 2015

How does the enable_ddl_logging parameter work to audit DDL?  Why is enable_ddl_logging superior to using a DDL trigger?


Answer:  There are many ways to enable DDL logging, see my notes on Oracle DDL auditingUsing enable_ddl_logging as a DDL Log Auditing Alternative is easy starting in 11g, and alternative to DDL triggers. If the enable_ddl_logging parameter is set to TRUE in 11g, then schema changes can be tracked in real time.  

DDL Logging is enabled with this command:

alter system set enable_ddl_logging=true;

The DDL logging data is written in XML format to the file located at $DIAG\rdbms\DBName\INSTNAME\log\ddl

Wrong changes can then be corrected easily by regenerating the corresponding database objects from the dictionary baseline. You can easily reverse-engineer the database and schema definitions, capture and version baselines, and compare databases and schemas or baselines.

Laurent Schneider adds this regarding a new and cool alternative offered in Oracle 11g. This option involves the use of enable_ddl_logging.

Setting enable_ddl_logging will allow the tracking of all DDL's in the alert log using the following:

ALTER SYSTEM SET enable_ddl_logging=TRUE

Later, you issue create table:

create table t(x number)

and you see in the alertLSC01.log:

Tue Apr 05 14:43:32 2015
create table t(x number);

Remember the alert log is just there for backward compatibility, it is time you start looking in the xml file:

<msg time='2011-04-05T14:43:42.210+02:00' org_id='oracle' comp_id='rdbms'
msg_id='opiexe:3937:4222333111' client_id='' type='NOTIFICATION'group='schema_ddl'
level='16' host_id='srv01' host_addr='' module='TOAD Beta'
<txt>create table t(x number)

There is not really much more there but the module, which indeed reveals someone is using TOAD to access my database !

Unfortunately for many shops, enable_ddl_logging is an additional cost feature available only to Enterprise Edition users.  The Oracle docs note that you need to purchase the database lifecycle management pack to use enable_ddl_logging=true:

"The init.ora parameter ENABLE_DDL_LOGGING is licensed as part of the Database Lifecycle Management Pack when set to TRUE.

When set to TRUE, the database reports schema changes in real time into the database alert log under the message group schema_ddl. The default setting is FALSE.

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