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Accessing Large Amounts of Data: Key Technologies and Concepts in Modern Computing

This chapter focuses on critical components for efficiently accessing and managing large volumes of data in corporate environments. Key topics include channel subsystems, control units, Direct Access Storage Devices (DASD), RAID configurations such as RAID-5, and the importance of data sharing and management systems. Emphasis is placed on enhancing system stability and scalability, ensuring high processor utilization, and achieving reliable data retrieval. Understanding these concepts is essential for leveraging technology in data-intensive applications across distributed systems.

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Accessing Large Amounts of Data: Key Technologies and Concepts in Modern Computing

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  1. Chapter 6: Accessing large amount of data

  2. Chapter objectives • After completing this chapter, you should be able to describe the concepts of: • Channel subsystems • Control Units • DASD • RAID • Multiple allegiance/ PAV • Random access to data • Databases • Data sharing • DFSMS

  3. Introduction • The core function of a large-scale computing environment is to process corporate data.

  4. I/O Connectivity

  5. Channel Subsystem

  6. Control units • To execute channel commands • Protocol : CCW • Chain : an operation that consist of more than 1 CCW • Allow functionality beyond the power of the early mainframe processors • Beginning : 1 device to 1 control unit • Now : 1 device can connect to > 1 control unit

  7. Direct Access Storage Device (DASD) Architecture

  8. DASD Architecture (Cont...)

  9. Mapping for access to devices • UCBUnit Control Block • UCWUnit Control Word • CUCB Control unit control block • The CSS uses the UCW to find the CUCBs and decides which is the best channel/control unit pair to use for the operation.

  10. Mapping for access to devices (Cont...)

  11. DASD Subsystem A control unit may be connected to several channels, and a device may be connected to several control units. This capability is a reason for operational availibility andresilience. Between the control unit and the IBM System z an ESCON or FICON-Director can be connected in addition. That will increase the systems stability and scalability.

  12. Redundant array of independent disk (RAID) There is a variety of common and insignificant RAID-level. RAID-5 has a high I/O rate and a medium data rate. RAID-5 is used by the IBM DS8000 controller arrays in the majority of configurations.

  13. Reducing the number of logical volumes • Amount of Data  problem : to manage logical volumes  solution : DFSMS • Larger Volumes  problem : more I/O to each volume  solution : RAID BUT... Is not enough...

  14. Multiple allegiance(MA)/Parallel access volume(PAV) MA PAV

  15. Random access to data • RAID : First slow, as of next high-speed retrieval • Predictive loading : load the data into the CONTROL UNIT CACHE

  16. Databases • likely on relational databases • a single large server controlling all data request  not on mainframe (clients & server on different machine): • Good data integrity • Poor processor utilization  on mainframe (clients & server on same machine) : • Good data integrity • Good processor utilization

  17. The ability to share data for both reading and updating, from multiple programs that can be running on different physical machines. Data Sharing • Parallel Sysplex is required • with structures in the Coupling Facility (CF) providing the necessary mechanisms

  18. Data facility Storage Management System • Object Access Method (OAM) • Tape library • OAM uses a hierarchy: • DASD • Tape volumes with a tape library device • Optical volumes inside a library device

  19. Data placement and management • Performance • Space • Backup • Migration

  20. Summary • The New Mainframe and access large amounts of data: • Access large amounts data is required for a variety of applications • Requires a high processor utilization • High levels of reliability are needed • Tape media : high capacity, low cost, but slow and sequential • Quick data transfer rates are need

  21. Channel subsystem CKD Control block Control Unit DASD Data Sharing DFSMS FBA Logical address PAV RAID Key terms in this chapter

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