ord_subtract(Set2, Set1, New).

F.2.33 library(persistency)

current_persistent_predicate/1	True if PI is a predicate that provides access to the persistent database DB.
db_assert/1	Assert Term into the database and record it for persistency.
db_attach/2	Use File as persistent database for the calling module.
db_attached/1	True if the context module attached to the persistent database File.
db_detach/0	Detach persistency from the calling module and delete all persistent clauses from the Prolog database.
db_retract/1	Retract terms from the database one-by-one.
db_retractall/1	Retract all matching facts and do the same in the database.
db_sync/1	Synchronise database with the associated file.
db_sync_all/1	Sync all registered databases.
persistent/1	De