DIRMAINT - Directory Maintenance

Enhanced Definition

`DIRMAINT` is a key component of the `z/VM` operating system on IBM mainframes, providing an automated and secure way to manage the `z/VM` user directory. It allows system administrators to define, modify, and delete virtual machines (VMs) and their associated resources (CPU, memory, DASD, network) without direct manual editing of the `z/VM` directory file. While `DIRMAINT` is specific to `z/VM`, it is crucial for managing the virtualized environment where `z/OS` systems often run as guests. DIRMAINT is a z/VM system service that provides centralized, automated management of the z/VM user directory. It allows z/VM system administrators to define, modify, and delete virtual machines (VMs) and their associated resources within the z/VM environment. While not a z/OS utility, it is critical for managing the underlying virtualization layer when z/OS runs as a guest operating system under z/VM.

Key Characteristics

- Automated Directory Management: Provides a structured and command-driven interface to automate the creation, modification, and deletion of z/VM user directory entries, which define virtual machines.
- Security and Control: Enforces granular security policies and access controls for directory modifications, ensuring that only authorized administrators can make changes to virtual machine configurations.
- Resource Allocation: Manages the allocation of virtual resources, such as virtual CPUs, virtual memory, virtual DASD volumes, and network adapters, to individual z/VM guest operating systems.
- Command-Driven Interface: Primarily managed through CP (Control Program) commands and DIRMAINT-specific commands issued by administrators, often via the VM console or RSCS (Remote Spooling Communications Subsystem).
- Batch and Interactive Modes: Supports both interactive command execution for immediate changes and batch processing for larger, scheduled, or scripted directory updates.
- Configuration Management: Stores z/VM directory information in a structured format, typically within DMDIRL files, which DIRMAINT processes to update the active z/VM directory.

Use Cases

- Provisioning New Virtual Machines: Rapidly create new z/VM guest operating systems, including new z/OS instances, Linux on z servers, or other z/VM guests, by defining their directory entries and resource allocations.
- Modifying VM Resources: Dynamically adjust the virtual CPU count, memory size, or virtual DASD allocation for existing virtual machines to adapt to changing workload demands or performance requirements.
- Deleting Obsolete VMs: Securely remove virtual machine definitions and associated virtual resources when they are no longer needed, ensuring proper cleanup of the z/VM environment.
- Automating System Administration: Integrate DIRMAINT commands into scripts or automated procedures for routine z/VM directory management tasks, enhancing operational efficiency.
- Managing Guest z/OS Environments: Define and manage the virtual environment (e.g., virtual CPUs, memory, I/O paths) for z/OS systems running as guests under z/VM, allowing for flexible z/OS deployments.