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There's actually two kinds of databases in this world.. File based and client/server databases.
File-based databases are the most simple type and the most common in small business. With a file-based database, a client maps a drive to a server and actually opens up the file containing the database on that mapped drive. When you do a search, you actually have to read in the entire database index from the drive, search it, then return the results and retrieve the data. This means you've got a HUGE amount of data transferring across the network, as the PC is doing the grunt work of searching the database. MS Access is a great example of how this works. In general, if you HAVE to map a drive letter to run the app, this is what you've got.
Client/Server databases are far more efficient and work better on a WAN. With a file-based database, a user sends a specific query to a database server. The DB server then does the work to perform the search on the database on it's local hard drive. The only thing that it sends back are the results and the client doesn't have to do much work. MS SQL server and Oracle are good examples of a client/server database. If you don't have to map a drive letter to run the app, this is probably what you've got.
<Instructor mode off>
I know that Peachtree is a file-based database. You shoud look at your database size on the server and see how big it is. Your worst case for performance should be roughly the time it takes to transfer that entire database across your WAN, plus quite a bit of overhead - I usually factor in about 30% on a VPN, 10% on a regular frame relay network. If you've got a 1Mb/s DSL line, transferring a 1MB database (which is 8 Mb, since 1 byte = 8 bits) is 8 seconds. Assume the circuit is 50% utilized and you're at 16 seconds. Add your 30^ overhead and you're at 21 seconds. Be generous - Say 30 seconds for a 1 MB database. If you've got a 30MB DB (which is certainly not uncommon for Peachtree) you're looking at about a 900 second response, or 15 minutes.
Just do the math - How big is the Peachtree database? How many users sharing how much bandwidth?
What I'm getting at is that a VPN and a WAN is a considerable investment. Be very sure to know your requirements and your limitations up front and set the proper expecations for your management. Without that, they will probably expect the response time at the remote sites to match that on the same network as the server, obviusly not something that's possible.
One easy sell - Use a Windows 2000 server in multi-user Terminal Server mode. It's very fast for end users, easy on bandwidth (~40Kb/s per user) and will offer much snapper resposne time than running the app across the WAN. Spending $3K on hardware/software once is a lot cheaper than needing to spend an extra $500/month for higher bandwidth to your offices.
If all else fails.. Test!
- G