C++Builder 5 Developers Guide

Deploying DataSnap is fairly easy. You have to find the correct set of DLLs and packages for your client application and include DataSnap itself (which consists of only MIDAS.DLL for DataSnap). There are no database drivers and no additional setup, only your client and MIDAS.DLL . You might need to register the server on your client machine as well, or at least the type library for the server ”see the "Accessing the Server Remotely" section which is covered in the next chapter.

You also need to purchase an official license. A MIDAS 2 license was pretty expensive at U.S. $5,000.00 per hardware server. You are allowed to run as many MIDAS 2 servers on a machine as you want and can. MIDAS 3 and DataSnap have a new lower-than-ever deployment license model, which incidentally has no effect on the MIDAS 2 licensing model (another reason to upgrade your MIDAS 2 applications to MIDAS 3). A MIDAS 3 or DataSnap license for an unlimited server is now only U.S. $299.95. As a result of this much lower price, Borland no longer offers a per-seat client license, making the licensing scheme not only much cheaper, but easier as well.

When do you need to purchase a DataSnap license? That depends on the DataSnap data packet (sent from the provider to the ClientDataSet or XMLBroker and back). In his DataSnap licensing article on the Borland Community site, John Kaster (Borland Developer Relations) has formulated two rules:

1. If the DataSnap data packet goes from one machine to another by any means, a license is required.

2. If the DataSnap data packet always stays on the same machine, you do not need a license.

Note that "by any means" includes copying to a floppy disk, using email, copying from one hard disk to another, backing up from one machine and restoring on another then resolving the data, and so on. Basically, this means any method of transferring the data packet from one machine to another (including retyping or a WAP connection).

This greatly reduced license fee is a tremendous opportunity for C++Builder 6 developers who need to develop n - tier solutions. Previously, clients had serious problems with the MIDAS 2 license fees ( especially if you had to prove all benefits first), but now I have little reluctance suggesting a multitier DataSnap approach.

And the future might be even better: Delphi 7 Studio (just released at the time of writing) has extended the DataSnap license by including a free deployment of DataSnap applications with Delphi 7 Enterprise or Architect. This means that if you've purchased a copy of Delphi 7 Enterprise (or Architect), you already paid for the DataSnap license of all DataSnap applications that you can build with that. Only for Delphi 7 and Kylix 3, I'm afraid. But C++Builder 7 will most likely contain a similar license schema. Stay tuned