I just fell over an issue with DBISAM on Windows 2000 that may be useful
to others to know about. My code has the following line:

if UpdateTable.Locate('msID;msXID;msState',
        VarArrayOf([n64ID, szXID, etsActive]), []) then

On XP, this works fine. Run on Win2000 it fails with 'Invalid variant
type'. After setting up the remote debugger, I've now pinned this down to
the fact that I have Int64 fields, and Windows 2000 doesn't support these
as variants. I think it is happening when DBISAM is returning the field
set, not in the call. There is a comment in line 329 of the Delphi 2007
Variants.pas that explains this, and you can set the global variable
OleVariantInt64AsDouble to true to overcome this. I've not tried this as
yet.

I figure that this may explain some unexplained errors, and it took me a
few hours to pin down (mostly getting the remote debugger to work!).

/Matthew Jones/

> OleVariantInt64AsDouble

Hmm, I just turned this on, but it still has the exception. This is going
to be a long one I can tell.

/Matthew Jones/

Okay, it seems that VarArrayOf is happy to take the Int64 value as-is,
with no conversion. DBISAM then gets a copy of the array, and that is
passed to Windows for copying. Windows 2000 then barfs on the Int64 type.

/Matthew Jones/

Okay, I tried using the VarUtils code instead of the Windows versions, and
it doesn't support anything beyond varLongWord which oddly enough is
varInt64. That's no help then.

At this point, I have to ask if anyone knows about compatibility of DBISAM
v4 Int64 fields and Windows 2000. It looks to me like it becomes quite
hard to use them reliably. I may have to specify that XP is the only
supported OS.

For now, I'm stuck.

/Matthew Jones/

Matthew,

<< At this point, I have to ask if anyone knows about compatibility of
DBISAM v4 Int64 fields and Windows 2000. It looks to me like it becomes
quite hard to use them reliably. I may have to specify that XP is the only
supported OS. >>

As far as I know, they should work fine with Windows 2000.  However, I did
find this:

http://qc.borland.com/wc/qcmain.aspx?d=8858

It may be that the Variants unit is using the OLEVariant type at some point
for the array elements and, therefore, the issue.

--
Tim Young
Elevate Software
www.elevatesoft.com

I too found that page, and it is what made me give up. I'm surprised to be
the first to find this for DBISAM, but it may be worth noting for
ElevateDB. It is a VCL limitation, but it is worth knowing about for In64
field use.

/Matthew Jones/

Matthew,

<< I too found that page, and it is what made me give up. I'm surprised to
be the first to find this for DBISAM, but it may be worth noting for
ElevateDB. It is a VCL limitation, but it is worth knowing about for In64
field use. >>

I'll have to do some more testing to find out exactly what the problem is
before I document it.

--
Tim Young
Elevate Software
www.elevatesoft.com

It isn't hard to check - the failure comes quite soon. I just put in a
breakpoint and then stepped into it. I'm sure you don't need the other
fields - locating on a single Int64 value, but making the VarArray, is all
you need. And Windows 2000 of course!

/Matthew Jones/

Matthew,

<< It isn't hard to check - the failure comes quite soon. I just put in a
breakpoint and then stepped into it. I'm sure you don't need the other
fields - locating on a single Int64 value, but making the VarArray, is all
you need. And Windows 2000 of course! >>

Yeah, that's the tough part.  I've got Windows 2000, but I need to find a
machine to install it on.

--
Tim Young
Elevate Software
www.elevatesoft.com

See the VMWare thread on your discussion newsgroup. 8-)
I'd offer my VM, except that all the code is on my main PC and I was
remote debugging.

/Matthew Jones/