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Maximizing Data Access Efficiency in Large Computing Environments

Explore concepts such as Channel Subsystems, RAID, Data Sharing, DFSMS, and more to optimize data access in a mainframe environment. Learn about control units, DASD architecture, and the importance of data integrity.

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Maximizing Data Access Efficiency in Large Computing Environments

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  1. Chapter 6: Accessing large amount of data i.e. Big Data

  2. Objectives Be able to describe the concepts of: • Channel subsystems • Control Units • DASD • RAID • Multiple allegiance/ Parallel Access Volumes (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. ESCON is an optical fiber, half-duplex, serial interface FICON has replaced ESCON in current deployments because of FICON's technical superiority (especially its higher performance) and lower cost. FICON is a network of Fibre Channel devices which allows many-to-many communication, device name lookup, security, and redundancy

  4. I/O Connectivity

  5. Channel Subsystem and System Assist Processors (SAP)

  6. Control units • To execute channel commands • Protocol : CCW • CCW Chain : an operation that consist of more than 1 CCW • Allow functionality beyond the power of the early mainframe processors... minimize interrupts • 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 Channel SubSystem uses the UCW to find the CUCBs and decides which is the best channel/control unit pair to use for the operation. “What's the best path”

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

  11. DASD Subsystem A control unit may be connected to several channels, a device may be connected to several control units. The reason is 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. (N+1 plus distributed Check Char) 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 relational databases • a single large server controlling all data request  not on mainframe (clients & server on different machines): • Good data integrity • Poor processor utilization  on mainframe (clients & server on same machine) : • Good data integrity • Good processor utilization

  17. Data Sharing The ability to share data for both reading and updating, from multiple programs that can be running on different physical machines. • 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) • OAM uses database/DASD, tape, and optical technologies to manage the storage and retrieval of objects. • 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

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