Q188710: File Locking Behavior in FPNW
Article: Q188710
Product(s): Microsoft Windows NT
Version(s): winnt:3.51,4.0
Operating System(s):
Keyword(s):
Last Modified: 11-JUN-2002
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The information in this article applies to:
- Microsoft Windows NT Server versions 3.51, 4.0
- Microsoft Windows NT Server, Enterprise Edition version 4.0
- Microsoft File and Print Services for NetWare version 3.51
- Microsoft Services for NetWare version 4.0
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IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:
Q256986 Description of the Microsoft Windows Registry
SUMMARY
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This article describes the file locking behavior of Microsoft File and Print
Services for NetWare (FPNW). It also describes registry entries that can be used
to modify the default behavior.
MORE INFORMATION
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To maintain data integrity, file locking is used by applications to ensure that
a file or a region within the file cannot be accessed by another application at
the same time. When an exclusive lock is set on a file, the file cannot be
opened for read or write access by any other application, and a sharing
violation will result.
Network or multiple user-aware applications often must allow access to one or
more files for multiple users at the same time, especially in the case of
executable files. This can be done by opening files that do not require write
access for shared read-only access.
Some older applications tend to open files for exclusive use when, in fact,
shared access to the file would be preferred. Novell NetWare servers work around
this problem by using the Shareable file attribute to indicate that a file can
be opened for shared access, even when an application requests exclusive access
to the file.
When a file on a NetWare server is marked as Shareable, requests to open a file
for exclusive use are translated to Read/Write Deny None, allowing multiple
clients to open the same file for read and write access. However, if a client
specifies that the file should be opened with Deny Read and Deny Write access,
the NetWare server will grant exclusive access to the file for that client, even
with the Shareable attribute set.
While there is not an equivalent file attribute in Windows NT to the NetWare
Shareable attribute, FPNW does provide compatibility for older applications by
emulating the behavior of the Shareable attribute settings. FPNW does this by
globally marking all files on an FPNW volume as Shareable, but requiring a
separate request for exclusive write access before allowing a write to a file
that has been opened by multiple clients.
WARNING: If you use Registry Editor incorrectly, you may cause serious problems
that may require you to reinstall your operating system. Microsoft cannot
guarantee that you can solve problems that result from using Registry Editor
incorrectly. Use Registry Editor at your own risk.
There are several registry entries that can be used to modify the default file
locking behavior with FPNW. They are located in the following registry key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\FPNW\Parameters
EmulateShareableFlag REG_DWORD 0 to 3
Default: 0
This affects how FPNW grants access to files that are opened for exclusive
access. Valid values are 1-3. Meanings of these values are listed below:
NCPSRV_COMPATIBILITYOPEN_DENYNONE (1)
All requests for Read-only Exclusive are mapped to Read/Write Deny None. If the
same client later opens the file for write purposes, the same handle is used.
FPNW ensures that only one client at a time has the file open for write. This
allows NetWare clients to run programs concurrently, and enables setup programs
that open the file for write, when they already have it open exclusively for
read, to run correctly. However, Microsoft clients or local clients can modify
the file without FPNW knowing about it because FPNW only has it open as
Read/Write Deny None. Also, clients using a file for synchronization or clients
that must have the file exclusively may encounter difficulty. This option is
recommended only for administrators who are sure they do not have applications
that will experience problems with this mode. This value is equivalent to the
Shareable bit being set on a NetWare server.
NCPSRV_COMPATIBILITYOPEN_DENYWRITE (2)
This is the default mode. In this mode, all requests for Read-only Exclusive are
translated to Read/Deny Write. This enables most older programs to be loaded
concurrently from multiple clients. However, requests for write exclusive cannot
be folded into existing read-inclusive requests, so some setup programs fail in
this mode.
NCPSRV_COMPATIBILITYOPEN_EXCLUSIVE (3)
This is the strictest option. When clients request exclusive use of a file, they
get exclusive use. NetWare clients cannot load the same executable files at the
same time because one of them will have it open exclusively. The file is opened
Read/Write Exclusive even if the client requests Read- only Exclusive. This mode
usually causes the most errors, but it is the only way to enable some
applications to function. This value is equivalent to the Shareable bit being
not set on a NetWare server.
NCPSRV_COMPATIBILITYOPEN_DEFAULT (0)
If a value of 0 is specified (or if no value is specified), the server defaults
to DenyWrite (2).
ReturnShareableFlag REG_DWORD 0 or 1
Default: 1
This indicates whether FPNW sets the Shareable property globally for all files in
all volumes on the server. The default is set to 1, which enables the Shareable
property.
EnableNtfsShareable REG_DWORD 0 or 1
Note: This registry value is incorrectly documented as EmulateNtfsShareable in
the Service for NetWare online help file.
This value enables per-file Shareable attribute to be set. If set to 0, or on
volumes that do not use NTFS, volume-wide shareable processing as specified by
EmulateShareableFlag is used.
If set to 1, administrators can set the Shareable flag on a per-file basis on
NTFS volumes, and the registry value for EnableNtfsShareable is ignored. For
files marked with the Shareable flag set, files are opened with Read/Write Deny
None. If a file is marked as not Shareable, files are opened with Read/Write
Exclusive.
FPNW does not currently ship with a utility to set the Shareable attribute. To
set the Shareable attribute, use the Flag.exe utility that can be found in the
PUBLIC directory on your NetWare server.
LockRetryCount REG_DWORD 0 to 100
Default: 5
When FPNW encounters an error opening a file, it will wait 600ms, then retry the
operation. This value specifies the number of times FPNW retries an open on a
file if the result of the open is that the file is in use.
OplockBreakWait REG_DWORD 0 to 240
Default: 60
Oplocks are used to enable write caching for compatibility mode opens (shared
read/write access). This value specifies the time in seconds that the server
waits for a client to respond to an oplock break request. Smaller values can
allow detection of crashed clients more quickly.
REFERENCES
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Complete information on available FPNW registry entries can be found in the
Service for NetWare online help file, Ms-sfn.hlp, on the CD-ROM in the
Online.doc folder and in the Administrator's Guide for File and Print Services
for NetWare version 3.51.
Additional query words:
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Keywords :
Technology : kbWinNTsearch kbWinNT351search kbWinNT400search kbWinNTSsearch kbWinNTSEntSearch kbWinNTSEnt400 kbWinNTS400search kbWinNTS400 kbWinNTS351 kbWinNTS351search kbServicesNetware400 kbServicesNetwareSearch kbFPNW351
Version : winnt:3.51,4.0
Issue type : kbinfo
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