User's Guide

Part V. The SQL Anywhere Programming Interfaces

Chapter 38. The WSQL HLI Interface

A Dynamic Link Library (DLL) is a collection of functions which are available to any program. DLL's are different from regular applications in that they are unable to execute on their own. They are always called from another application or DLL.

The main benefits of DLL's are:

• their ability to be shared by many independent applications at the same time (DLL's are a global resource).
• they provide a high level of abstraction. An application does not need to know how the DLL works to use it.
• their high upgradeability. If a new version of a DLL is released you should be able to use the new one immediately, without modifying, recompiling or relinking your software.
• their ease of use. In some programming environments all you have to do is declare which DLL you are using. Calling DLL functions is then identical to calling normal language functions. (DLL's are sometimes called plug-and-play for this reason.)

The WSQL HLI DLL is a shared system resource---it can be used by multiple applications. However, internally, all resources such as database connections, statements and cursors are managed on a per task basis. Thus, there will not be any name conflicts between various applications using the DLL.