he internal schema describes how the data will be physically stored and accessed, using the facilities provided by a particular DBMS. For example, the data might be organized so that all the insurance policies belonging to a given customer were stored close together, allowing them all to be retrieved into the computer's memory in a single operation. The conceptual schema (sometimes called the logical schema) describes the stored data in terms of the data model of the DBMS. In a relational DBMS, the conceptual schema describes all relations that are stored in the database The external schemas specify views that enable different users of the data to see it in different ways. As a simple example, some users of policy data might not require details of the commission paid. By providing them with a view that excludes the Commission Rate column, we would not only shield them from unwanted (and perhaps unauthorized) information, but also insulate them from changes that might be made to the format of that data.