Understanding the file system structure in OpenVMS is crucial for efficient file management and system administration. This section will cover the hierarchical organization of files and directories, the different types of file systems supported by OpenVMS, and the key concepts related to file storage and retrieval.

• Root Directory: The top-level directory in the file system hierarchy.
• Subdirectories: Directories within the root directory that can contain files and other subdirectories.
• Files: The basic unit of storage, which can be documents, executables, scripts, etc.

• ODS-2 (On-Disk Structure Level 2): The traditional file system used in OpenVMS.
• ODS-5 (On-Disk Structure Level 5): An enhanced file system that supports longer file names and a broader character set.

• Logical Volumes: A logical representation of storage that can span multiple physical disks.
• Physical Volumes: Actual physical disks that store data.

• File Names: Consist of a name and an optional extension, separated by a period (e.g., FILENAME.TXT).
• Version Numbers: OpenVMS supports multiple versions of the same file, indicated by a version number (e.g., FILENAME.TXT;1).

The OpenVMS file system is organized in a hierarchical structure, similar to a tree. Here is an example of a typical file system hierarchy:

• [ROOT]: The root directory of the file system.
• [SYS$SYSROOT]: Contains system-related directories.
  • [SYS$SYSTEM]: System files and executables.
  • [SYS$COMMON]: Common files shared across the system.
  • [SYS$SPECIFIC]: Files specific to the current system.
• [USER]: User directories.
  • [USER1]: Directory for user1.
  • [USER2]: Directory for user2.
• [DATA]: Data directories.
  • [PROJECT1]: Directory for project1.
  • [PROJECT2]: Directory for project2.

Let's create a directory structure and navigate through it using DCL commands.

• CREATE/DIRECTORY: Command to create a new directory.
• SET DEFAULT: Command to change the current working directory.
• SHOW DEFAULT: Command to display the current working directory.

1. Create a directory structure under [USER2] with subdirectories [USER2.DOCS] and [USER2.SCRIPTS].
2. Navigate to [USER2.DOCS] and create a file named README.TXT.

• CREATE/DIRECTORY [USER2.DOCS]: Creates the DOCS directory under USER2.
• CREATE/DIRECTORY [USER2.SCRIPTS]: Creates the SCRIPTS directory under USER2.
• SET DEFAULT [USER2.DOCS]: Changes the current working directory to DOCS.
• CREATE README.TXT: Creates a new file named README.TXT in the current directory.

In this section, we covered the hierarchical structure of the OpenVMS file system, the different types of file systems, and the key concepts related to file storage. We also provided practical examples and exercises to help you understand how to create and navigate directories in OpenVMS. Understanding the file system structure is fundamental for efficient file management and system administration in OpenVMS.