NetWare Loadable Modules (NLMs) are the building blocks used to customize the NetWare OS. NLMs are built to run in server memory with the NetWare OS (OS or protected address space). A program you can load and unload from server memory while the server is running. For instance dsrepair.nlm could be loaded on a Netware server in order to perform health check and other operations related to the NDS (Novell Directory Services) or eDirectory as it’s called nowadays.