Page Set, pages, and files
Date: Sun, 18 Dec 2005 04:12:10 GMT
Message-ID: <590036d0837a8_at_uwe>
Recently, I study the database system theory using "Introduction to Database Systems, 8th Ed" by C.J. Date
Question: (refer to regenerated information that follows) 1. The mapping between files and page sets is maintained by the file manager. True/False
2. Statement 1: Each page set will contain zero or more files. Is the page set the above statement refer exclusively to the free-space page set?
3. Can a file be contained in more than one page set?
Locating a specific piece of data in the database and presenting it to the user involves several distinct layers of software. (refer to Fig. 1).
(Request (Request (Disk I/O stored record) stored page) operation) DBMS -------------------> File -----------------> Diskfrom disk)
-----------------> Stored
<------------------- manager <----------------- manager <--- -------------- database (Stored record (Stored page (Data read returned) returned)
Fig. 1: The DBMS, file manager, and disk manager.
- First, the DBMS determines what record is required, and asks the file manager to retrieve that record.
- The file manager in turn determines what page contains the desired record, and asks the disk manager to retrieve that page.
- Finally, the disk manager determines the physical location of the desired page on the disk, and issues the necessary disk I/O request.
The above information is available in PDF format (Date App D online.pdf) at: ftp://ftp.aw.com/cseng/authors/date/eight/AppD/
Thanks for replying.
Regards,
Pedestrian
Received on Sun Dec 18 2005 - 05:12:10 CET