Introduction to the new mainframe: Large-Scale Commercial Computing © Copyright IBM Corp., All rights reserved. Chapter 2: Capacity

Introduction to the new mainframe © Copyright IBM Corp., All rights reserved. 2 Chapter objectives At the end of this chapter you should be able to describe: Mixed workloads SLA PR/SM and LPAR Parallel Sysplex Storage concepts and management Measuring capacity

Introduction to the new mainframe © Copyright IBM Corp., All rights reserved. 3 Definition of Capacity Capacity has several definitions: 1. The potential or suitability for holding, storing, or accommodating 2. The facility or power to produce, perform, deploy or, simply process

Introduction to the new mainframe © Copyright IBM Corp., All rights reserved. 4 Elements required for capacity (1/2) Any computer system, from a single-user PC to a multi- thousand user IBM System z mainframe performs work in the following stages: 1.Load a program from a storage device, normally a disk, to central storage 2.Process the instructions in the program 3.Load any required data from disk or tape into central storage 4.Process the data and send the results to the desired end point

Introduction to the new mainframe © Copyright IBM Corp., All rights reserved. 5 Elements required for capacity (2/2) The relevant components to perform these steps and therefore for capacity estimation & planning are: Processors Central storage Access input/output storage (for example disk or tape) Also the network to these devices has to be considered

Introduction to the new mainframe © Copyright IBM Corp., All rights reserved. 6 Many servers Few Servers Many servers : Data retention ? Locking across servers ? Connectivity ? Few servers (IBM System z): Large volumes of data: best in 1 place No rewitting needed of applications 1 total system

Introduction to the new mainframe © Copyright IBM Corp., All rights reserved. 7 Mixed Workload The approach to run mixed workload on one single system comes from the fact that in modern processor chips it is very unlikely, in a commercial environment, that one program could keep a processor fully utilized over a longer period of time. For example, running jobs for Online customers, Online in-house users and Batch work on the same system.

Introduction to the new mainframe © Copyright IBM Corp., All rights reserved. 8 Service Level Agreement A Service Level Agreement (SLA) is an agreement between a service provider and a recipient, generally the server owner and a business unit. SLAs are the baseline for capacity, availability and performance measurements and ratings. Example: 95% of ATM transactions are completed in less than one second. 90% of daily reports are completed by 6 A.M.

Introduction to the new mainframe © Copyright IBM Corp., All rights reserved. 9 Managing the system to the SLA Managing CPU Managing Disk Storage concepts (the address space) -> see next slide Real storage mangement

Introduction to the new mainframe © Copyright IBM Corp., All rights reserved. 10 Address space The Line 24 Bit systems The Bar 31 Bit systems

Introduction to the new mainframe © Copyright IBM Corp., All rights reserved. 11 Architecture, running work & capacity Program Status Word (PSW) Interrupts Machine check Restart Program Check I/O Supervisor call (SVC) External Supervisor call Selection of work to run on a CP Dispatching priority CP utilization balance

Introduction to the new mainframe © Copyright IBM Corp., All rights reserved. 12 Several servers on 1 physical machine LPAR Planning for downtime Software Hardware

Introduction to the new mainframe © Copyright IBM Corp., All rights reserved. 13 IBM System z – Parallel Sysplex ESCON/FICON Coupling Facility SYSPLEX Timer Shared Data Z9 BC Z9 EC Z9 BC Parallel Sysplex

Introduction to the new mainframe © Copyright IBM Corp., All rights reserved. 14 Measurements Central Processor usage Central storage usage Access to disk storage

Introduction to the new mainframe © Copyright IBM Corp., All rights reserved. 15 Summary Capacity Complex when you are : In a mixed workload On a large-scale commercial environment Different workloads different requirements well defined set of SLAs needed SLAs are also helpfull for: Measurement of capacity bottlenecks the planning of capacity upgrades.

Introduction to the new mainframe © Copyright IBM Corp., All rights reserved. 16 Key terms in this chapter 24-bit 64-bit Address space Capacity Central storage CP Downtime I/O Interrupt LPAR Mixed Workload Parallel Sysplex PR/SM PSW Real Storage SLA SVC The Bar The Line Virtual Storage