File Locking Behavior in FPNW (188710)

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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.

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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 (

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 (

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 (

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 (

If a value of 0 is specified (or if no value is specified), the server defaults to DenyWrite (2).
ReturnShareableFlag REG_DWORD 0 or 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

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.