The iPhone Client Object API defines server-side and client-side exceptions.
Server-Side Exceptions
A server-side exception occurs when a client tries to update or create a record and the Unwired Server throws an exception.
Client-Side Exceptions
The HeaderDoc for the Client Object API lists the possible exceptions for the iPhone client.
Attribute Datatype Conversion
When a non-nullable attribute's datatype is converted to a non-primitive datatype (such as class NSNumber, NSDate, and so on), you must verify that the the corresponding property for the MBO instance is assigned a non-nil value, otherwise the application may receive a runtime exception when creating a new MBO instance.
Operation Name Conflicts
Operation names that conflict with special field types are not handled.