The database objects (tables, indexes, etc.) that existed as of time
t0 may have changed so that
db.db does not equal db.db0.
The database db.db continues to read data from dbspaces
A, B and
C as long as the tables that existed at time
t0 exist and as long as they contain some
unmodified rows of data that existed as of time t0.
Even if or when this is no longer true, db.db will
continue to open A, B and
C unless they are dropped from
db.db, which is only allowed if they are empty from
db.db's point of view.