Why DA?

Integrates Zope transaction mechanisms, so if Zope throws an exception the RDBMS rolls back
Allows creation of object in ZMI, storing connection credentials (username, password, ip address etc.)
Generally one RDBMS connection per Zope thread. Some DA’s are single threaded, meaning only one query can execute at a time (eg zODBC)

Integrates Zope transaction mechanisms, so if Zope throws an exception the RDBMS rolls back