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SMB2, SMB3 and Opportunistic Locking

Datafile Software Solutions

SMB2, SMB3 and Opportunistic Locking


Datafile uses an ISAM database which may be affected by the use of Opportunistic Locking and SMB2/3 on later versions of Microsoft clients.

Datafile has several hundred other clients using the same infrastructure – i.e. Windows 7/8 clients with Windows 2008/2012 Server - without issue. However, if you do experience issues, evidence of which would include frequent audit of file messages during updates, it is advised you speak to your hardware support agent with regards disabling these Microsoft protocols.

This Microsoft Knowledge article details the registry key settings for disabling SMB2/3

http://support.microsoft.com/kb/2696547

This Microsoft Knowledge article details the registry key settings for disabling Opportunistic Locking

http://support.microsoft.com/kb/296264

For later versions of Server 2016 and Server 2019 then the SMB2 / Oplocks could still needs disabling but this is done in a slightly different way.

There’s an option Leasing Mode against folder/drive that allows you to set SMBShare – where would set to none.

Windows 10 RS3 and Windows Server 2016 RS3 allow a special oplock override workaround now for these scenarios

SMB3 shares now havean option called "LeasingMode". This allows admins to stop leases & oplocks, like SMB1.

Leasing Mode has three options in Powershell New-SmbShare / Set-SmbShare : None, Shared and Full

Full = default SMB3
Shared = grant read-caching lease but not write or handle-caching
None = no oplocks or leases, like modified SMB1

So, if you’re trying to get rid of SMB1 but have an app that requires no oplocks (and therefore SMB1), you can use SMB3 now. If you run ISAM databases in an app, this can help interoperability


It requires Windows Server 2016 or Windows 10 hosting the share, and they must be at least 16215 build.

Link: https://support.microsoft.com/km-kh/help/4034314/smbv1-is-not-installed-windows-10-and-windows-server-version-1709


  • Release ID: Standard