To replicate Updates and Deletes in Merge Apply mode, Data Replication requires source tables to have a logical primary key. The Applier uses this logical primary key to uniquely identify rows on the target. If source table definitions include primary keys or unique indexes, Data Replication uses these keys or indexes as the logical primary key. However, the Applier did not find a primary key or unique index with all of its columns supplementally logged for a source table in the configuration. Consequently, the Applier will apply each Update as a pair of Delete and Insert operations for the table.