Integrated File System Introduction
Use UDFS through the integrated file system interface
A UDFS can be accessed through the integrated file system interface using either the OS/400 file server or the integrated file system commands, user displays, and APIs. In using the integrated file system interface, you should be aware of the following considerations and limitations.
Case-sensitivity in an integrated file system UDFS
You can specify whether object names in the UDFS will be case-sensitive or case-insensitive when you create it.
When you select case-sensitivity, uppercase and lowercase characters are distinguished when searching for object names. For example, a name that is supplied in all uppercase characters will not match the same name in which any of the characters are lowercase. Therefore, /home/MURPH/ and /home/murph/ are recognized as different directories. To create a case-sensitive UDFS, you can specify *MIXED for the CASE parameter when using the CRTUDFS command.
When you select case-insensitivity, the server does not distinguish between uppercase and lowercase characters during searches for names. Therefore, the server would recognize /home/CAYCE and /HOME/cayce as the same directory, not as two separate directories. To create a case-insensitive UDFS, you can specify *MONO for the CASE parameter when using the CRTUDFS command.
In either case, the file system saves the same uppercase and lowercase forms in which the user enters object names. The case-sensitivity option only applies to how the user searches for names through the server.
Path names in an integrated file system UDFS
A block special file (*BLKSF) represents a UDFS when the entire UDFS and all of the objects within it need to be manipulated. If your UDFS resides on the system or on a basic user ASP, block special file names must be of the form
/dev/QASPXX/udfs_name.udfswhere XX is the ASP number where you store the UDFS, and udfs_name is the unique name of the UDFS within that ASP. Note that the UDFS name must end with the .udfs extension.
If your UDFS resides on an independent ASP, block special file names must be of the form
/dev/asp_name/udfs_name.udfswhere asp_name is the name of independent ASP where you store the UDFS and udfs_name is the unique name of the UDFS within that independent ASP. Note that the UDFS name must end with the .udfs extension.
Path names for objects within a UDFS are relative to the directory over which you mount a UDFS. For example, if you mount the UDFS /dev/qasp01/wysocki.udfs over /home/dennis, then the path names for all objects within the UDFS will begin with /home/dennis.
Additional path name rules:
- Each component of the path name can be up to 255 characters long. The full path name can be up to 16 megabytes long.
- There is no limit to the depth of the directory hierarchy other than program and server space limits.
- The characters in names are converted to UCS2 Level 1 form (for *TYPE1 directories) and UTF-16 (for *TYPE2 directories) when the names are stored (see Name continuity). Refer to *TYPE2 directories for more information about the directory formats.
Links in an integrated file system UDFS
Objects within a UDFS allows multiple hard links to the same object and fully supports symbolic links. A symbolic link can create a link from a UDFS to an object in another file system.
See Link for a description of links.
Use integrated file system commands in a UDFS
All of the commands that are listed in Perform operations using CL commands and the displays that are described in Perform operations using iSeries menus and displays can operate on a user-defined file system. There are some CL commands that are specific to the user-defined file system and other mounted file systems in general. The following table describes them.
Table 6. User-Defined File System CL Commands
Command Description ADDMFS Add Mounted File System Places exported, remote server file systems over local client directories. CRTUDFS Create UDFS Creates a user-defined file system. DLTUDFS Delete UDFS Deletes a user-defined file system. DSPMFSINF Display Mounted File System Information Displays information about a mounted file system. DSPUDFS Display UDFS Displays information about a user-defined file system. MOUNT Mount a file system Places exported, remote server file systems over local client directories. This command is an alias for the ADDMFS command. RMVMFS Remove Mounted File System Removes exported, remote server file systems from the local client namespace. UNMOUNT Unmount a file system Removes exported, remote server file systems from the local client namespace. This command is an alias for the RMVMFS command.
- You must mount a UDFS before any integrated file system commands can operate on the objects that are stored in that UDFS.
Use integrated file system APIs in a UDFS
All of the C language functions that are listed in Perform operations using APIs can operate on a user-defined file system.
- You must mount a UDFS before any integrated file system commands can operate on the objects that are stored in that UDFS.
Graphical user interface for a UDFS
iSeries Navigator, a graphical user interface on your PC, provides for easy and convenient access to UDFSs. This interface enables you to create, delete, display, mount, and unmount a UDFS from a Windows client.
You can perform operations on a UDFS through iSeries Navigator. Basic tasks include:
- Create a new user-defined file system.
- Mount a user-defined file system.
- Unmount a user-defined file system.
Create an integrated file system UDFS
The Create User-Defined File System command (CRTUDFS) creates a file system that can be made visible through the integrated file system namespace, APIs, and CL commands. The ADDMFS or MOUNT commands place the UDFS "on top" of the already-existing local directory. You can create a UDFS in an ASP or independent ASP of your choice. You can also specify case-sensitivity.
Delete an integrated file system UDFS
The Delete User-Defined File System command (DLTUDFS) deletes an existing, unmounted UDFS, and all the objects within it. The command will fail if you have mounted the UDFS. Deletion of a UDFS will cause the deletion of all objects in the UDFS. If you do not have proper authority to delete all of the objects within a UDFS, then none of the objects will be deleted.
Display an integrated file system UDFS
The Display User-Defined File System (DSPUDFS) command presents the attributes of an existing UDFS, whether mounted or unmounted. The Display Mounted File System Information (DSPMFSINF) command will also present information about a mounted UDFS as well as any mounted file system.
Mount an integrated file system UDFS
The Add Mounted File System (ADDMFS) and MOUNT commands make the objects in a file system accessible to the integrated file system namespace. To mount a UDFS, you need to specify *UDFS for the TYPE parameter on the ADDMFS command.
- A UDFS on an independent ASP can not be mounted over.
Unmount an integrated file system UDFS
The unmount command makes the contents of a UDFS inaccessible to the integrated file system interfaces. The objects in a UDFS will not be individually accessible once the UDFS is unmounted. The Remove Mounted File System (RMVMFS) or UNMOUNT commands will make a mounted file system inaccessible to the integrated file system namespace. If any of the objects in the file system are in use (for example, a file is opened) at the time of using the command, you will receive an error message. The UDFS will remain mounted. If you have mounted over any part of the UDFS, then this UDFS cannot be unmounted until it is uncovered.
For example, you mount a UDFS /dev/qasp02/jenn.udfs over /home/judy in the integrated file system namespace. If you then mount another file system /pubs over /home/judy, then the contents of jenn.udfs will become inaccessible. Furthermore, you cannot unmount jenn.udfs until you unmount the second file system from /home/judy.
- A UDFS on an independent ASP can not be mounted over.
Save and restore an integrated file system UDFS
You have the ability to save and restore all UDFS objects, as well as their associated authorities. The Save command (SAV) allows you to save objects in a UDFS while the Restore command (RST) allows you to restore UDFS objects. Both commands will function whether the UDFS is mounted or unmounted. However, to correctly save the UDFS attributes, and not just the objects within the UDFS, the UDFS should be unmounted.
Journal object changes in a UDFS file system
Objects in user-defined file systems can be journaled. The main purpose for journal management is to enable you to recover the changes to an object that have occurred since the object was last saved. For more information on journaling object changes in a UDFS file system, see Journaling support for integrated file system objects.
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