Re: ANN: NexusDB v2 Christmas Special - don't miss out!

eLion wrote:

1) Does the cross update offer (300USD) applies to BDE users ?
firebird users ?
Yes

2) I would use NexusDB to replace the BDE in some old applications
where maintenance should be low:
- Is there FULL COMPATIBLE TTable/TQUery components ?
As close to as possible. There are some small differences. But we've
had many customers very successfully converting their existing BDE
(paradox) based applications to NexusDB within a matter of hours.

- Can the tool provided be FULLY AUTOMATISED to import BDE databases
(with all indexes, fields, autoinc fields, data, blobs, integrity
reference...) ?
It is certainly possibly for you to write something that will fully
automatically convert the data for your existing clients from BDE to
NexusDB. There is a generic "Importer" available as binary from our
website that you can use as a start. The full source of that tool is
included with the source code version of NexusDB

- is there the equivalent of the BDE's dbi functions: I am using a
few, to rename a field, change the size of a field, lock some
records, ...
"equivalent", yes, exact same API, no

- do you have a CallBack system: when one application
on computer A is modifying data, can an application connected to the
same database on computer B be notified of the changes ?
Specifically like that, no. But there are things you can use to easily
implement whatever you need:

- The transport components that NexusDB utilizes for client-server
communication can operate in a fully 2 way fashion. The server is able
to send uninvited messages (not just replies to requests) to clients
using client initiated physical connections (preventing problems with
firewalls). One of our users has used that to write a "message plugin"
that can easily be used to send client to client messages. The source
for which is included in the Bonus folder of the NexusDB source
edition. You could use that to broadcast a message to all interested
clients once a client finished some change.

- There is a function on the TnxDatabase object that gives you with
very low overhead information about which of the tables you have
currently opened in that database have changed since you last called
the function:

procedure GetChangedTables(aList : TStrings);

Calling this function is very low overhead, involves only a single very
short message to the server and fills the passed in TStrings with the
names of the tables in this database that are currently opened through
the database and which have changed since you last called the function.
It's very easy to keep calling that function on a 2 or 5 seconds timer
and then performing refreshs on the affected TnxTable instances when a
change has been detected.

Using this approach is a lot lower overhead then having all changes
broadcasted directly as they happen to all clients.

- Is Local BDE SQL supported ?
"BDE SQL", no. But NexusDB does support SQL, strongly aligned with the
current SQL:2003 standard, and SQL is supported both in C/S mode as
well as in embeddeed mode.

3) How many files are used for one database ?
- is it one file per database ?
- one file per table ?
yes, plus 4 additional tables that are used to store SQL meta data,
views, stored procedures and such...

if one file per table, is there a version system possible for
table (a version number per table, that could be set/checked/updated)
Even better, each table allows you to store an unlimited number of
named streams (basically "per table blobs"). You can use that to store
something as simple as a version number or something as complex as a
binary structure representing some model information used by your
application.

4) How is the installation on client ? on server side ? configuration
? Can it be automatized via script (Inno Setup is used) ?
No installation is required on the client side. NexusDB is fully
implemented in Delphi, as such no DLLs or similar is required. The
client layer compiles fully into your application.

For cases where you only have a single client that directly accesses
the files (keep in mind here that file-sharing is specifcally not
supported, so this limites you to a single client accessing the files
at a time) the complete server engine including SQL support can be
directly compiled into your application, again, no DLLs or any other
external files required.

For the server side, all that is required is a single application (we
provide a precompiled nxServer.exe, in addition it comes with full
source ) All that you need to do with that server is to copy it
somewhere and start it. The server can also be run as an NT service.
The functionality is directly included in nxServer.exe. Simply starting
it once with /INSTALL as parameter will add it to the list of system
services.

In case you don't like our default server GUI or for some other reason
want to "roll your own". That's very simple:
http://www.nexusdb.com/tutorials/server_sbs.html

5) on your home page, http://www.nexusdb.com/showpage.asp?Id=125 ,
there is a column for NexusDB V2 developper, and one for NexusDB V2
Enterprise. I don't find anywhere on your web page info about
Enterprise version, nor the price...
Can you tell me more about enterprise version, and price ?
Sorry about that. The Enterprise features have been postponed to V3.
We'll need to update the website accordingly.

6) the source is included for everything ? included the server side ?
Yes. Full source for the server side is provided. Also, full source for
Enterprise Manager is provided, but that is not to be considered an
integral part of NexusDB, the source for EM is provided more as an
example. It does depend on a few 3rd party controls (primarily some
DevEx components and FastReport).

7) I tried to connect to your newsgroup without success.
It's often good to read what problems other users have, and how a
company is dealing with those...
Is there a way to access the newsgroup, or is it only for custommers ?
for how long, then ?
We don't have any other reports if problems accessing the newsgroups.
Our newsgroups are at news.nexusdb.com and are open to anyone. If you
have problems reaching the newsgroups (and maybe the website as well?)
there might be a fundamental problem with your internet access that
prevents you from reaching our server? That would explain why we
haven't received your mails.

Cheers,
Thorsten

--
Thorsten Engler
Principal Architect
Nexus Database Systems
.

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