How the server stores user-defined file systems

In a UDFS, as in the "root" (/) and QOpenSys file systems, users can create directories, stream files, symbolic links, and local sockets.

A single block special file object (*BLKSF) represents a UDFS. When you create a UDFS, the server also creates an associated block special file. You can only access the block special file through the Integrated File System generic commands, application programming interface (API), and the QFileSvr.400 interface. Block special file names must be of the form:

/dev/QASPxx/udfs_name.udfs

Where xx is the system or basic ASP number (1–32) where the user stores the UDFS and udfs_name is the unique name of the UDFS. Note that the UDFS name must end in the .udfs extension. If the UDFS is stored in an independent ASP, the block special file name will be of the form:

/dev/device-description/udfs_name.udfs

A UDFS exists only in two states: mounted and unmounted. When you mount a UDFS, you can access the objects within it. When you unmount a UDFS, you cannot access the objects within it.

In order to access the objects within a UDFS, you must 'mount' the UDFS on a directory (for example, /home/JON). When you mount a UDFS on a directory, you cannot access the original contents of that directory. Also, you can access the contents of the UDFS through that directory. For example, the /home/JON directory contains a file /home/JON/payroll. A UDFS contains three directories mail, action, and outgoing. After mounting the UDFS on /home/JON, the /home/JON/payroll file is inaccessible, and the three directories become accessible as /home/JON/mail, /home/JON/action, and /home/JON/outgoing. After you unmount the UDFS, the /home/JON/payroll file is accessible again, and the three directories in the UDFS become inaccessible.