Domain
In the context of IBM mainframe systems, a **domain** refers to a logical grouping or scope of control, resources, or authority within a system, network, or application environment. It serves to organize and manage related components, security policies, or administrative responsibilities, often tied to a specific subsystem, application, or operational boundary.
Key Characteristics
-
- Logical Grouping: Represents a conceptual boundary rather than a physical one, used to categorize and manage related resources (e.g., datasets, programs, network devices, users).
- Scope of Control: Defines the extent of authority or management for a particular set of resources or operations, often associated with a specific administrative team or function.
- Resource Management: Facilitates the organization and control of mainframe resources, making it easier to apply consistent policies for access, performance, and availability.
- Security Context: Frequently used in conjunction with security managers like
RACF(Resource Access Control Facility) to define security profiles and access control lists (ACLs) that apply to a specific set of resources or users. - Subsystem Specificity: Can be defined within specific mainframe subsystems (e.g.,
CICS,DB2,IMS,VTAM) to manage their respective resources and operations. - Administrative Boundary: Delineates responsibilities among system administrators, application support teams, or network operations personnel.
Use Cases
-
- Security Administration (RACF): Defining security domains in
RACFto group related resources (e.g., all productionCICSregions, allDB2databases for a specific application) and assign access permissions to specific user groups. - Network Management (VTAM/SNA): In
VTAM(Virtual Telecommunications Access Method), a domain refers to a set of network resources (terminals, applications, communication lines) that are managed by a singleACF/VTAMhost, enabling cross-domain communication for broader connectivity. - Application Resource Grouping: Grouping
CICSregions,IMScontrol regions, orDB2subsystems that support a particular business application into a logical domain for centralized monitoring, management, and problem determination. - Workload Management (WLM): Defining performance goals and resource allocations for workloads within a specific domain or service class, allowing
WLMto prioritize and manage system resources effectively. - System Automation: Grouping related automated tasks, alerts, and resources under a specific automation domain (e.g., using
SA z/OS) for centralized control and coordinated recovery actions.
- Security Administration (RACF): Defining security domains in
Related Concepts
The concept of a domain is closely related to security managers like RACF, where it forms the basis for defining resource groups and user access permissions, often mirroring organizational structures. In network architectures like SNA and VTAM, domains are fundamental for managing network resources and enabling communication between different VTAM hosts through cross-domain capabilities. Furthermore, mainframe subsystems such as CICS, DB2, and IMS often leverage domain-like concepts to logically group and manage their internal resources and applications for administrative and operational efficiency.
- Clear Delineation: Define domains with clear, logical boundaries based on business function, application ownership, or administrative responsibility to avoid ambiguity and simplify management.
- Principle of Least Privilege: Apply the principle of least privilege within each domain, ensuring that users and processes only have the minimum necessary access to resources within that domain.
- Consistent Naming Conventions: Implement consistent naming conventions for domains and the resources they encompass to improve readability, simplify automation, and reduce administrative overhead.
- Regular Review and Audit: Periodically review domain definitions, associated access controls, and resource assignments to ensure they remain accurate, secure, and aligned with current operational requirements.
- Comprehensive Documentation: Maintain thorough documentation for each domain, detailing its purpose, scope, included resources, and responsible administrative teams for effective knowledge transfer and troubleshooting.