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Database level supplemental logging is an Oracle requirement that ensures that the Oracle redo log on the source database contains the information required to describe all data changes completely. 

 Turning on supplemental logging ensures additional information is inserted into redo stream in order to facilitate replication. The extra level of overhead of adding this information into the redo log is generally less than 1%.

 Supplemental logging is not the default behavior of oracle database. It has to be enabled manually after the database is created. It can be enabled at two levels

1.  DATABASE LEVEL
2. TABLE LEVEL

Supplemental logging is also required in order to ensure the following items are replicated succesfullyreplicated successfully:

• chained rows
• clustered tables
• index organized tables (IOTs)

...

SQL> alter table '||owner||'.'||table_name||' add supplemental log data (primary key) columns; 

The supplemental log groups created by Dbvisit Replicate start with a G and then a random hex string: G575B4B0CC2E511E2A20CB8ADB3813

ALTER TABLE <table_name> ADD SUPPLEMENTAL LOG GROUP <log_grp1> 
(Column1,....,Column33) ALWAYS; 

ALTER TABLE <table_name> ADD SUPPLEMENTAL LOG GROUP <log_grp2> 
(Column34,....,Column66) ALWAYS; 
 
ALTER TABLE <table_name> ADD SUPPLEMENTAL LOG GROUP <log_grp3> 
(Column67,....,Column99) ALWAYS;

Verify supplemental logging

To check and monitor what supplemental logging has been turned on, the following query can be run

SQL> SELECT supplemental_log_data_min MIN, 
supplemental_log_data_pk PK, 
supplemental_log_data_ui UI, 
supplemental_log_data_fk FK,
supplemental_log_data_all "ALL" 
FROM v$database;

Modifying supplemental log behaviour

Please see variable _ADD_SUPLOG in Internal Variables on the default supplemental log behaviour and how to modify this.