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Chapter 6: Accessing large amount of data

Chapter 6: Accessing large amount of data. 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. Introduction.

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Chapter 6: Accessing large amount of data

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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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