The AK3 data segment is created in the functional acknowledgment
when an error is found in a data segment in the subject
document. If the functional acknowledgment is enabled, the
Functional Acknowledgment (997)
transaction set is created, and this data segment is created in this
transaction set as errors are found in data segments in the subject
document. The error code is stored in the Segment Syntax Error Code
(720) data
element. This data segment will not be present if no errors
are found.