To make the contents of a DCE LFS or non-LFS fileset visible and accessible to users in the DCE namespace, you must attach the fileset to the namespace through a mount point. In DFS, you use the fts crmount command to create a mount point for a fileset. A fileset is mounted automatically once a mount point is created for it, so you do not have to issue additional commands to attach the fileset. There are several types of mount points; the tasks in this topic all use regular mount points, which are the most common type.
A DFS mount point appears and functions like a regular directory, but structurally it is a special symbolic link that indicates the name of the fileset associated with the mount point. Each fileset has a directory structure whose root directory has the same name as the fileset's mount point. You can create standard subdirectories within the fileset's root directory. You can also create other mount points in the directory; these mount points look like subdirectories, but they are associated with files in their own filesets rather than with files in the mount-level directory's fileset.
When the Cache Manager traverses a path name to locate a file that resides in your cell, it begins at the cell's top-level fileset (root.dfs). As it traverses the file's path name, the Cache Manager accesses a different fileset whenever it encounters a mount point.
Most filesets are mounted with regular mount points. When the Cache Manager encounters a regular mount point in a read-only fileset, it attempts to access the read-only version of the fileset named by the mount point. It also attempts to access the read-only version of any fileset whose mount point it encounters further in the file's path name. However, if a fileset in the path name is not replicated, the Cache Manager accesses the read/write version of the fileset. From that point on, it continues to access the read/write version of each fileset it encounters in the remainder of the path name unless it is explicitly directed to access the read-only (or backup) version of a fileset.
Given how the Cache Manager traverses mount points, to be able to access the read-only version of a fileset, you must replicate all filesets mounted at higher levels in the file system hierarchy. In other words, you must create read-only copies of the fileset that contains the mount point for the fileset and all filesets above it in the file system. (See Using Mount Points for more information about the different types of mount points and how the Cache Manager accesses them.)