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Concurrent Domain Control Data Base Access Disclosure Number: IPCOM000105946D
Original Publication Date: 1993-Sep-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 2 page(s) / 38K

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Related People

Callaway, JR: AUTHOR [+1]


Disclosed is a method for controlling concurrent access to database files.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 84% of the total text.

Concurrent Domain Control Data Base Access

      Disclosed is a method for controlling concurrent access to
database files.

     Information about IBM OS/2*LAN Server domain objects is kept in
a number of database files that reside on the domain controller.
These files are referred to as the Domain Control Database (DCDB)
files.  Access to the DCDB files is either done locally, via calls to
the DCDB access functions made by the full-screen interface (FSI)
code, by redirected i/o to the server DCDB files from remote
machines, or by calls to local and remoted Application Program
Interfaces (APIs).  Since the functions that access the DCDB files
contain global (system-wide) data, concurrent execution through the
various paths is impossible.  Collisions occur, resulting in
incorrect data and protection exceptions.

     The DCDB access functions are called from many places within the
FSI.  Changing the interface to these functions would require many
changes to the FSI code.  The FSI relies on some of the global data
for error information, so elimination of all global data is not

     A unique solution to the problem was developed instead.  A
mapping layer, below the externalized entry points used by the FSI,
was created.  This layer handles the global data requirements of the
FSI, invoking as necessary the core DCDB functions.  Further, these
core functions were modified in such a way as to be reentrant

(simultaneously accessible by many threads...