Integration

The Tuxedo doc says:

>
a transaction processor is an example of a 3-tier client/server architecture, where the transaction processor
supports the application logic between the GUI front-end and the back-end resource managers.
Examples of resource managers are SQL databases, message queues, legacy applications, and
other back-end services.
>

Is this a general description of a Tuxedo ATMI application ?
Does this mean that for an Oracle Tuxedo + Oracle Database application all SQL statements must be executed by the Tuxedo tier with a Tuxedo ATMI API call ?

Thanks.