Editing DLL hell (section)

===Running conflicting DLLs simultaneously===
The solutions here consist of having different copies of the same DLLs for each application, both on disk and in memory.

An easy manual solution to conflicts was placing the different versions of the problem DLL into the applications' folders, rather than a common system-wide folder. This works in general as long as the application is 32-bit or 64-bit, and that the DLL does not use shared memory.  In the case of 16-bit applications, the two applications cannot be executed simultaneously on a 16-bit platform, or in the same 16-bit virtual machine under a 32-bit operating system.  [[Object Linking and Embedding|OLE]] prevented this before Windows 98 SE/2000, because earlier versions of Windows had a single registry of COM objects for all applications.

Windows 98 SE/2000 introduced a solution called ''[[side-by-side assembly]]'',<ref>{{Cite web |url=http://msdn2.microsoft.com/en-us/library/ms811700.aspx |title=Implementing Side-by-Side Component Sharing in Applications (Expanded) |publisher=Microsoft |access-date=3 January 2013 |archive-url=https://web.archive.org/web/20061210042506/http://msdn2.microsoft.com/en-us/library/ms811700.aspx |archive-date=10 December 2006}}</ref> which loads separate copies of DLLs for each application that requires them (and thus allows applications that require conflicting DLLs to run simultaneously).  This approach eliminates conflicts by allowing applications to load unique versions of a module into their address space, while preserving the primary benefit of sharing DLLs between applications (i.e. reducing memory use) by using memory mapping techniques to share common code between different processes that do still use the same module. Yet DLLs using shared data between multiple processes cannot take this approach.<ref>{{cite web |url=http://msdn.microsoft.com/en-us/library/h90dkhs0(VS.71).aspx |title=How do I share data in my DLL with an application or with other DLLs? |publisher=[[Microsoft]] |access-date=2008-11-11}}</ref>  One negative side effect is that orphaned instances of DLLs may not be updated during automated processes.