Oplocks are the way that SMB clients get permission from a server to locally cache file operations. If a server grants an oplock (opportunistic lock) then the client is free to assume that it is the only one accessing the file and it will aggressively cache file data. With some oplock types the client may even cache file open/close operations. This can give enormous performance benefits. When you set fake oplocks = yes, smbd8 will always grant oplock requests no matter how many clients are using the file. It is generally much better to use the real support rather than this parameter. If you enable this option on all read-only shares or shares that you know will only be accessed from one client at a time such as physically read-only media like CDROMs, you will see a big performance improvement on many operations. If you enable this option on shares where multiple clients may be accessing the files read-write at the same time you can get data corruption. Use this option carefully! no