You might need to define a new audience level for your Contact Optimization session.
Campaign administrators can create new audience levels. When you create an audience level,
Campaign creates a virtual contact history table in the
Campaign system tables. The administrator must map the
Campaign contact history table to a database contact history table (a “physical” contact history table). This step ensures that you have a record of customer contacts. Certain optimization rules are based on whether previous communications were made to a proposed contact. This information is stored in the database contact history table, therefore mapping the contact history tables is an important step.