Page Cache Management > Pager Interface Structure
The pager module implements a data structure named Pager. Each open database file is managed through a separate Pager object, and each Pager object is associated with one and only one instance of an open database file. (The object is synonymous with the database file.) The B+-tree module, to use a database file, creates a new Pager object, and uses the object as a handle to apply pager-level operations on the file. The pager module uses the handle to track down information regarding file locks, the journal file, the status of the database, the status of the journal, etc.