| 摘要 |
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. |
