Replication errors fall into the following categories:
Duplicate primary key errors Two users INSERT a row using the same primary key values, or one user updates a primary key and a second user inserts a primary key of the new value. The second operation to reach a given database in the replication system fails because it would produce a duplicate primary key.
Row not found errors A user DELETES a row (that is, the row with a given primary key value). A second user UPDATES or DELETES the same row at another site.
In this case, the second statement fails, as the row is not found.
Referential integrity errors If a column containing a foreign key is included in a publication, but the associated primary key is not included, the extraction utility leaves the foreign key definition out of the remote database so that INSERTS at the remote database will not fail.
This can be solved by including proper defaults into the table definitions.
Also, referential integrity errors can occur when a primary table has a SUBSCRIBE BY expression and the associated foreign table does not: rows from the foreign table may be replicated, but the rows from the primary table may be excluded from the publication.