4.2.3.2      Build a Dictionary in the Redo Data
A LogMiner dictionary must be built into the redo data so that the LogMiner component of SQL Apply can properly interpret changes it sees in the redo. As part of building LogMiner Multiversioned Data Dictionary, supplemental logging is automatically set up to log primary key and unique-constraint/index columns. The supplemental logging information ensures each update contains enough information to logically identify each row that is modified by the statement.

To build the LogMiner dictionary, issue the following statement:

SQL> EXECUTE DBMS_LOGSTDBY.BUILD;
The DBMS_LOGSTDBY.BUILD procedure waits for all existing transactions to complete. Long-running transactions executed on the primary database will affect the timeliness of this command.

The DBMS_LOGSTDBY.BUILD procedure uses Flashback Query to obtain a consistent snapshot of the data dictionary that is then logged in the redo stream. Oracle recommends setting the UNDO_RETENTION initialization parameter to 3600 on both the primary and logical standby databases.