Page "Transaction Processing Facility" Paragraph 13

Records that absolutely must be managed by a record locking process are those which are processor shared.

In TPF most record accesses are done by using record type and ordinal.

So if you had defined a record type in the TPF system of ' FRED ' and gave it 100 records or ordinals, then in a processor shared scheme record type ' FRED ' ordinal ' 5 ' would resolve to exactly the same file address on DASD-clearly necessitating the use of a record locking mechanism.