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

Introduction to the new mainframe © Copyright IBM Corp., 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

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

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

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

Introduction to the new mainframe © Copyright IBM Corp., 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

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

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

Introduction to the new mainframe © Copyright IBM Corp., 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.

Introduction to the new mainframe © Copyright IBM Corp., All rights reserved. 10 Mapping for access to devices (Cont...)

Introduction to the new mainframe © Copyright IBM Corp., 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.

Introduction to the new mainframe © Copyright IBM Corp., 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.

Introduction to the new mainframe © Copyright IBM Corp., 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...

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

Introduction to the new mainframe © Copyright IBM Corp., 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

Introduction to the new mainframe © Copyright IBM Corp., 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

Introduction to the new mainframe © Copyright IBM Corp., 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

Introduction to the new mainframe © Copyright IBM Corp., 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

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

Introduction to the new mainframe © Copyright IBM Corp., 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

Introduction to the new mainframe © Copyright IBM Corp., 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