In computer lingo, libraries are those storage slots that have helper codes and data. These codes and data are used for other independent programs. Libraries are designed in such a manner that sharing and modifications could be done in a modular fashion. A DLL or dynamic-link library is a module that includes data and functions that are used by other modules or applications.

The modular application facilitates frequent updating as and when required and also reapplying it over and again. When more than one application is using the same functions or shares the same DLL code, the DLL helps to reduce the memory overhead.
A DLL usually exports data, which is by and large used exclusively by its own functions. However, other modules can also read and write the address. An exported function in a DLL can be used by other modules as well as by the DLL defined function. Whereas, internal functions are called only by the DLL that defines the same function.

Common DLL problems

An extension DLL has often more related problems than a Regular DLL. An object defined the extension DLL is often unrecognized and cannot be serialized. A warning message often appears stating ‘class not defined’. Resources stored in the Extension DLL cannot be loaded properly. The cause to this is mostly because this extension DLL is not wired/linked to the object chain of regular DLL.

You can use the AppWizard Extension DLL code to create a CDynLinkLibrary object in the extension DLL. Any CDynLinkLibrary is wired into a default chain. You need to call this function once from each regular DLL that uses an extension DLL. When an extension DLL is loaded DllMain is loaded first and it executes even before any application starts.

Another common problem is the sharing inconsistency when you install a new FrontPage component DLL. Web Servers that are based on Windows environment sometimes are unable to overwrite the DLL i.e. modify it according to the specific requirement while loading/installing FrontPage components that have DLL implementation linked with the server. This particularly happens because the DLL file is locked and used by the Web Server itself.

A solution to this problem is setting a specific Windows Registry value. This value commands the loading and unloading of extension libraries with each command request. This process is used to avoid frequent termination and restarting of the servers each rime the files are shared. To avoid caching of extension libraries the value is set to zero and to help the server revert to normal function the value is reset to one. Each time the value is set/reset the server needs to be stopped and restarted.

Most Web Servers do not allow free extension libraries for their optimal functioning levels. This is particularly formulated to skip reading libraries from disk every time a page is loaded. However, the process of developing FrontPage component libraries requires stopping and restarting for testing the newly loaded Web Server every time a new version is installed.

To free the library you need to stop all services like www, ftp etc. The Internet Service Manager located on your Start menu will help you to accomplish this task. Whereas, on PWS you need to go to the Control Panel that helps to solve this issue. You need to stop the http service by pushing the stop button to refrain the server from using the DLL file and freeing the library.