To make a DCE LFS or non-LFS fileset visible in the DCE namespace, you must use the fts crmount command to create a mount point for it in the DFS filespace. Mount points create the appearance of a single, seamless file system even though different filesets are stored on different File Server machines. A fileset's contents are visible and accessible as files and directories in the filespace only when the fileset is mounted; they are not available if the fileset is not mounted. Once its mount point is created, a fileset is automatically mounted; you do not need to take any further actions or explicitly mount it again at any time in the future.
A mount point is a specific type of symbolic link stored in the file system. It acts as an association between a directory location and a fileset. The root of a fileset contains an actual directory structure, to which the Cache Manager assigns the name of the fileset's mount point. A fileset's root directory provides a path name for all of the files, subdirectories, and mount points contained in the fileset.
During file retrieval, the Cache Manager traverses a file's complete path name until it finds the file. When it encounters a mount point in a path name, the Cache Manager reads the mount point to learn which fileset is mounted at the mount point. It then contacts the Fileset Location Server to locate the fileset. As it traverses a path name, the Cache Manager interprets any additional mount points it finds until it reaches the fileset that contains the requested file.
Do not mount a fileset at more than one location in the file system. Creating multiple mount points can distort the hierarchical nature of the file system. The Cache Manager stores a single pointer to the directory that contains the root directory of each fileset; the Cache Manager can become confused about which path name to follow when searching for a file in a fileset with multiple mount points. This is true even if you specify the full path name of a file. Create multiple mount points for a fileset sparingly, in only a very limited number of troubleshooting and testing situations. Remove the extraneous mount points as soon as they are no longer necessary.
Different types of mount points exist. Types of Mount Points describes the different types of mount points in detail. Briefly, a mount point can be characterized by its
· Fileset type (read/write, read-only, or backup)
· Mount point type (regular, read/write, or global root)
The fts lsmount command can be used to examine mount points to determine their types and the filesets they name. The command displays the following message for each directory that is a mount point:
'directory_name' is a mount point for fileset 'fileset_name'
In the output, directory_name is the name of a directory (in this case, a mount point) that you specify, and fileset_name is the name of the fileset for which directory_name serves as a mount point. The command also provides the following information about the directory and fileset:
· A # (number sign) precedes the fileset name if the directory is a regular mount point.
· A % (percent sign) precedes the fileset name if the directory is a read/write mount point.
· An ! (exclamation point) replaces the fileset name if the directory is a global root mount point.
Do not create a symbolic link that begins with a # (number sign) or a % (percent sign) character. Because a mount point is a special type of symbolic link that uses these characters internally to identify its type, the Cache Manager becomes confused if it encounters a normal symbolic link that begins with one of these characters.
The fts delmount command is used to remove mount points. The fileset that is referred to by a removed mount point remains in existence, but its contents are not accessible until another mount point is created for it.
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