FOCUS and the RDBMS interact as follows:

1. Given a TABLE, Maintain, or MODIFY request, the adapter builds SQL statements that define the request in terms the RDBMS can understand.
2. Having received these SQL statements from the adapter, the RDBMS retrieves or updates data targeted by the request.
3. In response, the RDBMS sends the data (answer set) and/or return code back to the adapter, which in turn passes it to FOCUS for further processing (for example, CRTFORM display and value changes).

The following diagram illustrates FOCUS interacting with a DB2 data source: