Berkeley DB

Selecting a Queue Extent Size

In Queue databases, records are allocated sequentially and directly mapped to an offset within the file storage for the database. As records are deleted from the queue, pages will become empty and will not be reused in normal queue operations.To facilitate the reclamation of disk space, a queue may be partitioned into extents, and each extent is kept in a separate physical file. Extent files are automatically created as needed and destroyed when they are emptied of records.

The extent size specifies the number of pages that make up each extent. By default, if no extent size is specified, the queue resides in a single file and disk space is not reclaimed. In choosing an extent size, there is a tradeoff between the ...