The Sleep Mode is made to allow the end-users to write SQL statements that are not supported by Active Query Builder (DML, DDL) in the text editor.
This mode is enabled by default, but it might be disabled by setting the QueryBuilder.AllowSleepMode property to False. Switching to this mode is done automatically on assigning a not supported SQL query to the query builder. During this assignment, no parsing exceptions are thrown, but the QueryBuilder.SleepModeChanged event is fired.
The component in the "sleep mode" shows empty diagram pane and query columns grid. It switches this mode off on assigning a SELECT statement or when end-user starts to build a new query visually. In the second case, the QueryBuilder.QueryAwake event is fired. By handling this event, you may ensure that the user really wants to start building a new query, as this action will replace the previous non-supported SQL statement with a new one. You can deny this to prevent the loss.