In the world of IBM's z/OS operating system, SMS reigns supreme as the storage management subsystem of choice. Standing for "System Managed Storage," SMS automates the allocation and management of storage resources on a z/OS mainframe system. Here are some key features and functions of SMS that make it a must-have for storage administrators:

- Automated Storage Management: SMS automates many tasks related to storage management, such as volume allocation, data placement, and space management. This automation helps reduce administrative overhead and ensures efficient use of storage resources.

- Policy-Based Management: Administrators define storage policies and rules that dictate how data should be managed. These policies specify attributes such as storage classes, data migration criteria, and backup requirements. SMS then automatically applies these policies to manage data according to the defined rules.

- Storage Classes: SMS allows administrators to define different storage classes, each with its own characteristics and attributes. These storage classes help categorize data based on its importance, access frequency, retention requirements, and performance needs.

- Data Migration and Tiered Storage: SMS supports data migration between different storage tiers based on predefined policies. For example, less frequently accessed data may be automatically moved to lower-cost storage tiers, while frequently accessed data remains on high-performance storage.

- Space Management: SMS provides tools and mechanisms for monitoring and managing storage space usage. It helps ensure that storage resources are efficiently utilized and prevents storage shortages or overallocation.

- Backup and Recovery Integration: SMS integrates with backup and recovery solutions to automate data protection tasks. It allows administrators to define backup policies and schedules and automatically manages the movement of data to backup devices.

Overall, SMS simplifies storage management on z/OS systems by providing automation, policy-based management, and integration with other storage-related tasks. It helps organizations optimize storage resource utilization, improve data availability, and streamline administrative processes.