A database view of a database is created which provides a
transaction-consistent view of an existing database at a previous time.
Each database view contains all the information needed to, along with the
primary database, determine the contents of the primary database at a
previous time. The database view consists of a side file corresponding to
each data file in the primary database. The side files contain a copy of
all data from the corresponding data file which has been changed since
the database view was created. Sparse files may be used for the side
files in order to conserve space. Page table data is kept in order to
allow a quick determination as to whether the page from the primary
database has been modified and the old version stored in the database
view side file.