Re: [Fwd: File Locking and Permissions Issue]

Scott Lovenberg <scott.lovenberg@xxxxxxxxx> · Thu, 15 May 2008 06:34:35 -0400

Michael Heydon wrote:

Jack Lauman wrote:

<snip>

I compared the open files with one computer in Lacerte vs. two
computers in Lacerte and noticed one thing peculiar: when one computer
is using Lacerte, all files are opened with exclusive+batch oplocks
including Data1i07.dbf, however when 2 computers are running Lacerte, a
few files open without oplocks, notably data1i07.dbf.

I'm assuming that both users need to write to these files? Maybe I'm 

missing something but this seems to be entirely expected behaviour.

Oplocks allow a client to cache data rather than having to constantly 

sync to the server, obviously if there is more than one client doing 

this things break.

You could use fake oplocks to grant oplocks to all clients, but unless 

the application is designed for it (which I doubt it is) you will just 

wind up corrupting your data.

If the application is regularly opening and closing files (and 

therefore possibly being granted oplocks and then having them broken) 

you might find that performance improves by disabling oplocks 

altogether (well, performance for multiple users, performance for a 

single user would suffer).

<snip> I've attached both files to this message.  Any help in 

resolving this

matter would be greatly appreciated.

I think the list strips non-text attachments, so no excel file. Not 

that I think it's terribly important since it sounds like your system 

is working exactly as it should.

Thanks,

Jack Lauman

*Michael Heydon - IT Administratorr *
michaelh@xxxxxxxxxxxxx <mailto:michaelh@xxxxxxxxxxxxx>

Just a thought, but if you're using an enterprise distro, you might be 

able to cheat the system by granting fake oplocks and using a 

distributed file system, but there still could be coherency and race 

conditions under some circumstances.  It would probably depend on your 

usage patterns for the application as to whether you could push the 

envelope and get away with it.  If your access is mostly write once and 

read thereafter, it might be alright.  YMMV.

I've always had issues with Office 2000 and multiple users.  You can 

almost feel the whiplash of Access or Excel slowing down the moment a 

second connection is established.  Though, I must admit, I've never had 

corruption due to concurrent access, so it at least works for the speed 

trade-off.  Unless the app slows down to a crawl, it's probably better 

safe than sorry.  Especially if you're potentially rolling a corrupted 

file in to your backups.

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