Overview

There have been some reports of intermittent issues using MicroStation V8i and later when accessing a DGN and/or DWG files stored on shared network drives using the Windows file sharing protocol SMBv2 or SMBv3.

The SMBv2 network protocol is the default protocol for accessing Windows file shares when the workstation is running Windows Vista or later and the server is running Windows Server 2008 or later. SMBv3 is the default for workstations running Windows 8 with servers running Windows Server 2012.

There are some non-Microsoft servers and devices that support SMBv2 / SMBv3, therefore if you are using a non-Microsoft server or device, please check with that vender for what network protocols it supports.

How to tell

If you are experiencing a SMBv2 / SMBv3 related issue you may intermittently see one of the following error messages when trying to open or save a DGN or DWG file on a network share:

Opening a file…“Unable to open design file. Please contact your local site administrator or technical support provider for further assistance.”

Opening a file…“[DGN File name] is not in a recognized file format”

Saving a file…“Unable to save design file. Most likely, Network connection was lost. Do you want to Retry?”

If you retry the operation several times it should complete successfully. This should not be confused with a problem specific to the file. If the file doesn’t open or save after several tries, then there may be a problem with the actual file.

SMBv2 / SMBv3 related issues are mostly seen when:

• Opening and saving files when a large number of users are working in the same folder on the server.
• Working on highly referenced design files with several other users.
• Working in high latency network environments with several other users (E.G. multi-site WAN environment).

The problem stems from changes Microsoft made to the way file locking and caching work under SMBv2 / SMBv3 causing applications to hold on to files longer than the older SMBv1 (The protocol used by default in Windows XP and Windows Server 2003 and earlier).

Examples workflows that could see the error...

1. User A is editing design file A.dgn which is referenced by design file B.dgn, someone opens design file B.dgn (read-write or read-only) within a few sec of a change being saved to design file A.dgn. Depending on the file size and timing, one user will get access to the file and the other will not, resulting in one of the users getting one of the errors above.
2. User A makes a change to a design file and MicroStation writes an updated thumbnail to a file and then tries to save a design change to the file. Another system sees the thumbnail has changed and locks the file to read the new thumbnail before MicroStation can write its changes to the file causing the save to fail for the first user. The other system could be running any application that would display a thumbnail including Windows Explorer.
3. Two users open different master design files that share reference files at the same time. One of the users gets one of the above errors because the reference file can’t be read.

What to do?

To alleviate this problem, there is a fix in a later MicroStation SS3 build.  If you believe you are experiencing the issue described in this tech note please contract Bentley Technical Support.  This situation is being further evaluated and investigated to be addressed in future released builds.

Note:  When a user tries to save a file and encounters a network lock with a build with the fix the user may see the save operation take up to 15 seconds longer than normal. MicroStation will be unresponsive during this time. If a save operation takes longer than 15 it is likely to see one of the above error messages.  This is expected for network environments with large latency.

If you are not able to upgrade MicroStation the workaround is to disable SMBv2 / SMBv3 which will cause Windows to fall back to SMBv1. More information on SMBv2 / SMBv3 and how to disable it can be found at http://support.microsoft.com/kb/2696547

Note: There are also a number of non SMBv2 / SMBv3 related issues that can cause these errors such as Anti-virus scanners, file backup services, VSS. You may want to consider disabling SMBv2 / SMBv3 on a few workstations to see if it improves those users experience before considering a larger change.

See Also

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