Occasionally, a gap can occur during the capturing of changed data for a source table. For example, if you shut down the Capture program and then cold start it, it deletes all rows from the CD table. In this case, updates might be made that the Capture program does not capture. Or, any updates that were in the CD table could have been deleted (by the cold start) before the Apply program could replicate them.
When a gap exists, the Apply program attempts a full refresh unless the target table is noncomplete. If the Apply program cannot perform a full refresh, data integrity could be lost.