Hierarchical File System (HFS)

MPE/iX file system

Prior to Release 4.5, the MPE/iX file system includes accounts, groups, and files. This is the traditional MPE file system structure that you are used to.

Figure 2-1 “MPE/iX File System (Prior to Release 4.5)”shows an example of two accounts on an MPE/iX system:the SYS and ACCT1 accounts. The SYS account contains the PUB and GRP1 groups. The groups PUB and GRP1 coexist as equals. GRP1 cannot be a subgroup of PUB or vice versa. The ACCT1 account has only one group, also called PUB. Files exist within the groups. The files cannot be located directly under the accounts. They can only exist in groups.

Figure 2-1 MPE/iX File System (Prior to Release 4.5)

MPE/iX hierarchical file system

Beginning with MPE/iX Release 4.5, the file system structure of MPE/iX is enhanced with the introduction of the MPE/iX hierarchical directory structure. This was accomplished by integrating the MPE/iX HFS structure within and around the traditional MPE file system. This provides the benefits of both structures to MPE/iX users without forcing them to choose one environment or the other.

MPE/iX hierarchical directory services present an integrated view of the file system. All file system components exist under one directory called the root directory (designated as /). Directories are structures that can contain files and other directories.

MPE/iX accounts and groups are considered to be special directories that serve as hierarchical directories while continuing to serve as traditional MPE accounts and groups. To ensure that the classic MPE file system view still exists, accounts can only be created under the root directory, and groups can only be created under accounts.

Figure 2-2 “MPE/iX File System (Release 4.5 and Later)” shows the MPE/iX file system structure introduced as of Release 4.5. In the figure, the boxed portion shows how the traditional account, group, and file system structure fits into the HFS structure. Notice that hierarchical directories and HFS files can now fall under traditional MPE groups. For example, the figure shows lowercase_file as being located in the PUB group of the ACCT1 account. Also notice that the directory dir3 falls under the GRP1 group in the SYS account. The traditional MPE accounts, groups, and files can and do coexist with the HFS files and directories. As the figure shows, as of Release 5.0, files and directories can exist under accounts.

Figure 2-2 MPE/iX File System (Release 4.5 and Later)

Although accounts and groups are directories, they maintain their unique characteristics as well. This manual still refers to accounts and groups where necessary for clarity. When discussing characteristics of directories in general (including accounts and groups), this manual uses the term "directory." When referring specifically to a directory that exists outside of the traditional account-group structure, this manual uses the term "HFS directory."