Page Set, pages, and files

From: Pedestrian Ooi <u16758_at_uwe>
Date: Sun, 18 Dec 2005 04:12:10 GMT
Message-ID: <590036d0837a8@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       ----------------->      Disk


----------------->     Stored 

               <-------------------  manager <-----------------  manager  <---
--------------  database             
                (Stored record                      (Stored page
(Data read
                    returned)                                returned)

from disk)

Fig. 1: The DBMS, file manager, and disk manager.

1. First, the DBMS determines what record is required, and asks the file manager to retrieve that record.
2. The file manager in turn determines what page contains the desired record, and asks the disk manager to retrieve that page.
3. 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 Sat Dec 17 2005 - 22:12:10 CST