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List:       sqlite-users
Subject:    Re: [sqlite] network access problem
From:       Pavel Ivanov <paivanof () gmail ! com>
Date:       2010-05-27 18:00:42
Message-ID: AANLkTik4wZK96nVrbNYj85eYJr8D8QPrRpzMHAso5Oml () mail ! gmail ! com
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> a)  There are no other processes or connections accessing this db. There are no \
> journals or writing being done to any db across this or any connection.  Both in \
> the virtual world and the host pc.

You didn't get Roger's words correctly. Although you don't have any
other processes or journals SQLite itself doesn't know that. So it
should always obtain a SHARED lock on database. Also while opening
database it should check if database has RESERVED lock on it (to
understand if it needs to rollback journal). As you can see in SQLite
sources all these operations result in some sequence of read and write
locks on some ranges of bytes inside database file. So apparently your
virtual box reacts on those locks differently than normal Windows
system would have and SQLite doesn't understand how to deal with that.


Pavel

On Thu, May 27, 2010 at 9:29 AM, Art <azerger@yahoo.com> wrote:
> a)  There are no other processes or connections accessing this db. There are no \
> journals or writing being done to any db across this or any connection.  Both in \
> the virtual world and the host pc. b) Running windows xp pro 32bit in VB.  Parent \
> PC is windows 7 ultimate 64 bit. c) Yes, when the folder's permission in the vb \
> settings were set to r/w for the shared folder, it worked.  When set to read only \
> it fails. 
> Thank you,
> Art,
> ==========================
> From: "Black,
> Michael (IS)" <Michael.Black2@ngc.com>
> 
> One thing to be clear on.
> What OS are you running in your Virtualbox?  I hope it's not
> unix-flavored as that could/would be your problem.
> 
> Also...you
> didn't say that read/write worked over the UNC path...only that
> read-only failed.
> Michael D. Black
> ---------------------------------------
> From: Roger Binns <rogerb@rogerbinns.com>
> Just because
> you are opening the database read only does not mean that other
> connections in the same or different processes are.  Consequently it is
> still
> necessary to do locking.  Additionally if a journal exists then it may
> need to be rolled back which requires writing to the database and deleting
> the journal, the latter also requiring write permissions to the directory.
> 
> Roger
> ------------------------------
> From: Art <azerger@yahoo.com>
> Thanks for the suggestions:
> 
> Sqlite Manager also
> fails.
> 
> This is a permission issue with the sql open api.  This
> is a "Shared Folder" under VirtualBox with "read only permission".  If
> the folder is tagged as full access then sql open works.
> 
> There
> should be no reason that the openv2 statement with read_only specified
> should  fail under these circumstances,
> 
> If this was a problem
> with virtualbox then you see their message board light up with complaints.  Its \
> not, no other apps have problems accessing files through vb shared folders!
> 
> Art.
> 
> ________________________________
> 
> Running in sqlite
> application in Virtual Box, attempt to open a database with sqlite from a shared \
> network folder \\Vboxsvr\testdata  however the open16 and openv2 (with read only)  \
> both fail --- rc = 14.  App opens file if moved locally to hard drive. 
> using latest version of sqlite3 3.6.23.1
> 
> this seems to be a bug in
> the open code of sqlite when accessing a file across a network.
> 
> Thank you,
> Art Zerger
> AZerger@yahoo.com
> =======================================
> From: "Griggs, Donald" <Donald.Griggs@allscripts.com>
> Hi Art,
> I just succeeded in opening a db with a UNC path, under Windows XP Pro, using
> the same version (3.6.23.1) with the command-line utility -- but I do
> NOT use virtual box.
> Does the command-line utility fail for you under virtual box?
> Might you attempt it without virtualbox?
> 
> Donald
> ------------------------------
> From: Kees Nuyt <k.nuyt@zonnet.nl>
> A VBox shared folder is not exactly the best example of
> "sharing over a network". The purpose of shared folders is
> to copy files to and from virtual machines in an easy way.
> I think the locking primitives of
> VBox shared folders are
> not 100%.  You could try again with NFSv4.
> --
> (  Kees Nuyt
> )
> c[_]
> ------------------------------
> From: Jean-Christophe Deschamps <jcd@q-e-d.org>
> I don't believe so: I use several bases which I open with MS short UNC
> syntax 200 times a day without any problem ever (using vanilla 3.6.23.1).
> 
> Your
> issue is elsewhere.  Make sure the account you use has enough
> rights to the destination folder and check you can
> access it with, for
> instance, a innocent application like a hex
> editor or a third-party
> SQLite manager.
> =======================================
> 
> 
> 
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> 
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