I have provided the first 3 records in full MARC as you requested. The retrieval facility comprises two services - Present and Segment . Present is a request to the Z-server to send certain records and Segment is the process of breaking a large number of records into smaller numbers for ease of transmission. Segment can also be applied to breaking very large records into parts. The Present service is more interesting to the librarian since it defines how records can be requested.
Segment is primarily of interest for optimising network transmission.
The parameters of this message deal with how many records, how they should be shown etc. ID A transient name for the result set. In version 3, the record format and data elements requested can be specified, depending on the record syntax used, to a high degree of detail. If the response records are to be segmented then the number and size of the segments is specified. When the target gets the Present request it responds with the records and some associated information.