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Browse Prior Art Database

Lock/Unlock Past End of File

IP.com Disclosure Number: IPCOM000099288D
Original Publication Date: 1990-Jan-01
Included in the Prior Art Database: 2005-Mar-14
Document File: 3 page(s) / 112K

Publishing Venue

IBM

Related People

Lindsey, AH: AUTHOR [+2]

Abstract

Disclosed is a special usage of the OS/2* and DOS file access function calls. When applied to the past the end of a file's physical data, the following are realized in a multiprocessing (such as OS/2) or Area Network (LAN) environment: update prevention via serialization of file accesses, concurrency via virtually unlimited concurrency compatible file accesses, via support for many varieties of locking resource utilization via minimization of open handles, and of performance impact via utilization of range locks.

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

Lock/Unlock Past End of File

       Disclosed is a special usage of the OS/2* and DOS file
access function calls.  When applied to the past the end of a file's
physical data, the following are realized in a multiprocessing (such
as OS/2) or Area Network (LAN) environment: update prevention via
serialization of file accesses, concurrency via virtually unlimited
concurrency compatible file accesses, via support for many varieties
of locking  resource utilization via minimization of open handles,
and of performance impact via utilization of range locks.

      All of the above characteristics can be easily obtained
standalone access methods by exploiting this  feature of OS/2 and DOS
operating systems.  The access method could immediately participate
in a data sharing environment any changes whatsoever to the existing
data files.

      Note:  Locking past the end of a file is not an error as in
the technical reference manual.

      When data sharing support is required, the technique of is
generally employed.  A lock on a file or a range within the file is a
semaphore which signals that data is in use.  However, the only way
the semaphore be seen is if an attempt is made to lock the same data
the existence of another lock.  When this occurs, a will display to
indicate that the data cannot be or modified at this time.  The user
attempting the lock must wait until the initial lock is released his
lock can be applied.  As long as all users of the observe the same
lock/unlock protocol, data accesses be serialized and inadvertent
overwrite due to accesses can be prevented.  This protocol is
generally the responsibility of the file method and does not require
any special attention on part of the users.

      DOS and OS/2 support lock/unlock function calls that a to have
exclusive access to a byte range associated a shared file.  When
using these function calls, users specify, among other parameters, a
four-byte offset and four-byte length to identify the region to be
locked.  The region can either be within the range of the file or,
expanded upon in this disclosure, outside the physical of the file.
To lock a region within the range a file is a common technique which
involves physical data  However, locking outside the boundary of a
file past the end of file) is supported under the OS/2 and
environments and may have important functional for applications which
support, or would benefit support...