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Browse Prior Art Database

Deleting Database Files

IP.com Disclosure Number: IPCOM000110605D
Original Publication Date: 1992-Dec-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 2 page(s) / 70K

Publishing Venue

IBM

Related People

Buquoi, GH: AUTHOR [+3]

Abstract

A method is described which determines when database files should be deleted and where the files are located.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Deleting Database Files

       A method is described which determines when database
files should be deleted and where the files are located.

      When an application deletes a database object (table or index),
the OS/2* Database Manager (DBM) does not physically delete the
file(s) at the time of the request.  Instead it truncates the file(s)
to zero length.  This is necessary because other processes may also
have the file(s) open.  The operating system will not allow a file to
be deleted when it is open.

      When an application connects to the database, the contents of
the Object Relocation File (ORF) are read into a set of linked lists
in memory.  These linked lists are collectively referred to as the
Table Object Location Linked List (TOLLL).

      In prior releases, at database termination (the last
application disconnects from the database) the Database Manager scans
the main database directory and locates all files with a zero length.
At this point in time, the files are physically deleted.

      This method will no longer work for two reasons:
      1) When a database object is spanned, each of the new file
parts is created.  Then the data is redistributed from the old parts
into the new parts.  If the number of new file parts is greater than
the number of pages in the old file parts, then one or more of the
new parts may be length 0.  The Database Manager can no longer assume
that all 0 length files should be deleted.
      2) Since table objects can be spanned into multiple
directories, each directory that contains database files must be
scanned.  The OS/2 provides AP...