1. Introduction to the new mainframe: Large-Scale Commercial Computing © Copyright IBM Corp., 2006. All rights reserved. Chapter 6: Accessing large amount of data

2. Introduction to the new mainframe © Copyright IBM Corp., 2006. All rights reserved. 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 to the new mainframe © Copyright IBM Corp., 2006. All rights reserved. 3 Introduction The core function of a large-scale computing environment is to process corporate data.

4. Introduction to the new mainframe © Copyright IBM Corp., 2006. All rights reserved. 4 I/O Connectivity

5. Introduction to the new mainframe © Copyright IBM Corp., 2006. All rights reserved. 5 Channel Subsystem

6. Introduction to the new mainframe © Copyright IBM Corp., 2006. All rights reserved. 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. Introduction to the new mainframe © Copyright IBM Corp., 2006. All rights reserved. 7 Direct Access Storage Device (DASD) Architecture

8. Introduction to the new mainframe © Copyright IBM Corp., 2006. All rights reserved. 8 DASD Architecture (Cont...)

9. Introduction to the new mainframe © Copyright IBM Corp., 2006. All rights reserved. 9 Mapping for access to devices  UCB Unit Control Block  UCW Unit 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. Introduction to the new mainframe © Copyright IBM Corp., 2006. All rights reserved. 10 Mapping for access to devices (Cont...)

11. Introduction to the new mainframe © Copyright IBM Corp., 2006. All rights reserved. 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 and resilience. 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. Introduction to the new mainframe © Copyright IBM Corp., 2006. All rights reserved. 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. Introduction to the new mainframe © Copyright IBM Corp., 2006. All rights reserved. 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. Introduction to the new mainframe © Copyright IBM Corp., 2006. All rights reserved. 14 Multiple allegiance(MA)/Parallel access volume(PAV) MAPAV

15. Introduction to the new mainframe © Copyright IBM Corp., 2006. All rights reserved. 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. Introduction to the new mainframe © Copyright IBM Corp., 2006. All rights reserved. 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. Introduction to the new mainframe © Copyright IBM Corp., 2006. All rights reserved. 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. Introduction to the new mainframe © Copyright IBM Corp., 2006. All rights reserved. 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. Introduction to the new mainframe © Copyright IBM Corp., 2006. All rights reserved. 19 Data placement and management  Performance  Space  Backup  Migration

20. Introduction to the new mainframe © Copyright IBM Corp., 2006. All rights reserved. 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. Introduction to the new mainframe © Copyright IBM Corp., 2006. All rights reserved. 21 Key terms in this chapter Channel subsystem CKD Control block Control Unit DASD Data Sharing DFSMS FBA Logical address PAV RAID