<i>How will be the access path built here?</i>
It will be what is known as “arrival sequence”. In general, the access path will be the physical sequence that records are stored on disk.
Note that physical sequence possibly have little relationship to the order that records were written to the file. E.g., if the REUSEDLT(*YES) attribute is set for the physical file, then normal add/change/delete maintenance can place new records into the physical positions of records that were previously deleted. File reorganization and various changes over the years can also affect the physical ordering on disk.
The basic rule is that the order of retrieval is not guaranteed unless you specify an order.