By default, opportunistic locking is enabled for server
message block (SMB) clients that run one of the Windows operating systems that
is listed in the "Applies to" section. Opportunistic locking lets clients lock
files and locally cache information without the risk of another user changing
the file. This increases performance for many file operations but may decrease
performance in other operations because the server that grants the
opportunistic lock must manage the breaking of that lock when another user
requests access to the file.Notes for Windows Vista
- The opportunistic locking registry keys are valid only for traditional SMB (SMB1). You cannot turn off opportunistic locking for SMB2. SMB2 was introduced in Windows Vista to enable faster communication between computer that are running Windows Vista and Windows Server 2008 or Windows Server 2008 R2.
- If you disable opportunistic locking, the offline files feature in Windows
This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
How to back up and restore the registry in Windows
The location of the client registry entry for
opportunistic locking has changed from the location in Microsoft
Windows NT. In later versions of Windows, you can disable opportunistic locking
by setting the following registry entry to 1:
OplocksDisabled REG_DWORD 0 or 1Note
Default: 0 (not disabled)
The OplocksDisabled entry configures Windows clients to request or not to request opportunistic locks on a remote
You can also deny the granting of opportunistic locks by setting
the following registry entry to 0:
EnableOplocks REG_DWORD 0 or 1Note
Default: 1 (enabled)
The EnableOplocks entry configures Windows-based servers
to allow or to deny opportunistic locks on
local files. These servers include workstations that share files.
addition, you can use the following values to tune opportunistic locking for
Windows-based computers that have granted opportunistic locks.
following value specifies the minimum link throughput that the server allows
before it disables raw and opportunistic locks for this connection:
MinLinkThroughput REG_DWORD 0 to infinite bytes per second
The following value specifies the maximum time that is allowed
for a link delay. If delays exceed this number, the server disables raw I/O and
opportunistic locking for this connection.
MaxLinkDelay REG_DWORD 0 to 100,000 seconds
following value specifies the time that the server waits for a client to
respond to an oplock break request. Smaller values allow detection of crashed
clients more quickly, but might potentially cause loss of cached data.
OplockBreakWait REG_DWORD 10 to 180 secondsNote
You must restart the computer for these registry changes to take