Data Replication requires DB2, Microsoft SQL Server, and Oracle source databases to log additional information in expanded log records to replicate Updates, resolve conflicts, and filter replicated rows. When you save a configuration, the Data Replication Console creates virtual indexes for the primary key definition, conflict resolution rules, and filtering conditions.

To record generated virtual indexes, Data Replication enables the logging of additional information for a source in the following ways:

For DB2 sources, Data Replication uses the DATA CAPTURE CHANGES option for all of the mapped source tables. This option causes DB2 to log full row images.
For Microsoft SQL Server sources, Data Replication enables Change Data Capture for all of the mapped source tables.
For Oracle sources, Data Replication enables supplemental logging for virtual index columns.

The Data Replication Console also enables additional logging for the virtual index columns or for the entire table, as appropriate for the source database. Data Replication generates index names based on the following criteria:

For a primary key definition that is based on a database primary key, the Data Replication Console names the index by the database constraint name.
For a primary key definition that includes all of the table columns, the index name consists of the table name followed by the _PK suffix.
For conflict resolution rules, the index name consists of the table name followed by the _Conflict_Resolution suffix.
For filtering conditions that you define on the
Map Columns
tab, the index name consists of the table name followed by the _WHERE suffix.
For filtering conditions that you define on the
Routing
tab, the index name consists of the table name followed by the _FILTER suffix.

The following datatypes are not supported for additional logging because full before and after images are not available for them:

For DB2 sources, BLOB, CLOB, DBCLOB, LOB, LONG VARCHAR, and LONG VARGRAPHIC datatypes
For Microsoft SQL Server sources, IMAGE, NTEXT, NVARCHAR(-1), TEXT, XML, VARBINARY(-1), and VARCHAR(-1) datatypes
For Oracle sources, BLOB, CLOB, LONG, LONG RAW, NCLOB, and RAW datatypes

Because these datatypes cannot be a part of a virtual index, you cannot use them to define a custom virtual index, a filtering condition, and conflict resolution rules.