Chapter 7: ClientServer Applications Step-By-Step

Overview

In the context of this chapter, Client/Server applications are accessing remote data, data that is not Visual FoxPro tables (DBF). More and more we are seeing CIOs and IT Managers require new applications use a SQL backend database. This architecture presents new challenges when deploying Visual FoxPro solutions. This chapter addresses these issues and presents some solutions for you to consider when you approach a deployment.

There is a time when you realize an application you support can no longer run properly using the same DBF data stores you have been using for the better part of two decades. It could be the fact one or more tables is approaching the two gigabyte limit, your customer is suffering through another index or table corruption, someone copied the DBF files, walked across the street, and loaded the data on their competitors machine, or the network is too bogged down caching indexes and records so the performance is suffering. Maybe it is your existing customer or a potential new customer asking if you can deploy a system based on SQL Server 2000, Oracle, Sybase, SQLAnywhere, Informix, MySQL, or DB2 because they heard it is the next big thing and their applications must be buzzword compliant. Regardless of the reason, deploying a client/server application is not difficult. There are numerous advantages and disadvantages of deploying a client/server application instead of a file server-based deployment (see Table 1 ). There are both similarities and differences to the workstation and traditional local area network (LAN) applications.

Table 1. The advantages and disadvantages of deploying client/server applications written in Visual FoxPro with a backend database server.

Advantages	Disadvantages
Royalty free application runtimes	Additional components to deploy and configure
Built-in security inside database	More complicated process to update structures in production
Scheduled jobs	Numerous connection techniques to understand and determine the best one to deploy with the application
Scalable solutions	2 GB database limit (with MSDE)
Potentially less network traffic	‚
Native replication and distributed data	‚
Online backups	‚
Market acceptability (buzzword compliant)	‚

This chapter is not going to address the different design architecture between a Visual FoxPro application accessing Visual FoxPro data and the same application needing to access a SQL backend database. We are going to address the differences in deploying a Visual FoxPro application accessing a SQL database backend. We use the term backend database and remote data interchangeably. Both of these are referring to a database server, either one of the products mentioned in the introductory chapter or another like product.

In many respects, the implementation is similar to the implementation of a Workstation installation detailed in Chapter 6: ‚“Workstation and Traditional LAN Applications Step-By- Step. ‚½ You can implement the application and the data using any of the scenarios discussed in chapter six. This chapter focuses on the data implementation and other issues you might face implementing a client/server application and how they might affect your deployment package. Our backend database experience is with SQL Server (both full and MSDE) so the examples and content are demonstrated with SQL Server. Most of the concepts easily carry over to other backend databases. Also, in our experience the majority of Visual FoxPro developers use SQL Server if they use a backend database.