[Harbour] Re: USE error ?

[Viktor Szakáts]

Hi,

Related to this: My app doesn't need exclusive mode, 
but there are still a few typical places where it is 
used: pack and reindex (and structure change) operations.
 
If POSIX doesn't support exclusive access, what is the 
recommended way to open a table for above operations 
if I want to avoid issues in multiuser scenarios?

Brgds,
Viktor

On 2010 Feb 1, at 14:48, David Arturo Macias Corona wrote:

> Przemek:
> 
> Something has changed for this case since Aug 2007 ?
> 
> "It mean that (in Linux) Harbour and xHarbour can not share dbf files ?"
> 
> Your last message included below
> 
> I do not found some reference for this difference between Harbour-xHarbour in doc\xhb-diff.txt
> 
> David Macias
> 
> 
> On Thu, 02 Aug 2007, David Arturo Macias Corona wrote:
> > >The application which was working in background keeping dbf file open
> > >was compiled by Harbour and blocked only other Harbour processes because
> > >Harbour and xHarbour use different methods to emulate DOS/Windows DENY
> > >flags in POSIX systems.
> > It mean that (in Linux) Harbour and xHarbour can not share dbf files ?
> 
> Now. It means that POSIX systems do not have EXCLUSIVE mode.
> Everything is open in SHARED mode. I added emulation for DENY
> flags but it's only emulation and I created two versions for
> such emulation. Harbour has both - xHarbour only one.
> But if user needs real portability then he has to create code
> working in SHARED mode only or sooner or later he will make
> sth what breaks POSIX locks semantic, f.e. he open and close
> already open file what clears all FCNTL locks set on this
> file by the same process using different file handle because
> kernel recognize them as pair: PID+INODE and both will be the
> same.
> I do not have time now for detail POSIX locks description and
> what are the differences between DOS/Windows and rest of normal ;-)
> world. Few years ago I sent such description to xHarbour.news
> and it should be in some archive.
> Probably sooner or later someone will add DOS DENY flag emulation
> directly to Linux kernels for easier implementation things like SAMBA
> server and in such case I'll also add it core code. Maybe it's already
> happened - I haven't time to trace kernel modification in last two
> years.
> 
> best regards,
> Przemek
> 
> 
> 
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