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description
Introduction to the new mainframe:Large-Scale Commercial Computing
© Copyright IBM Corp., 2006. All rights reserved.
Chapter 6: Accessing large amount of data
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Introduction to the new mainframe
© Copyright IBM Corp., 2006. All rights reserved.
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
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Introduction to the new mainframe
© Copyright IBM Corp., 2006. All rights reserved.
Introduction
The core function of a large-scale computing environment is to process corporate data.
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Introduction to the new mainframe
© Copyright IBM Corp., 2006. All rights reserved.
I/O Connectivity
CHANNEL SUBSYSTEM
CONTROLUNIT
PRINTER DASD
CONTROLUNIT
CPU CPU
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Introduction to the new mainframe
© Copyright IBM Corp., 2006. All rights reserved.
Channel Subsystem
Storage
CPU CPU
SAPSAP
Channel SubsystemEscon and Ficon
CU
CU CU
CUSwitch Switch
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Introduction to the new mainframe
© Copyright IBM Corp., 2006. All rights reserved.
Control units
To execute channel commandsProtocol : CCWChain : an operation that consist of more than 1
CCWAllow functionality beyond the power of the early
mainframe processors
Beginning : 1 device to 1 control unitNow : 1 device can connect to > 1 control unit
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Introduction to the new mainframe
© Copyright IBM Corp., 2006. All rights reserved.
Direct Access Storage Device (DASD) Architecture
head headheadhead data datadata
Gap, Sync
startsector
startsector
startsector
startsector
sector i-1 sector i sector i+1
Fixed Block Record Format
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Introduction to the new mainframe
© Copyright IBM Corp., 2006. All rights reserved.
DASD Architecture (Cont...)
Count, Key, Data (CKD) Format
Gap, Sync
countkeycountkeycount data datadata key
record i-1 record i record i+1startrecord
startrecord
startrecord
startrecord
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Introduction to the new mainframe
© Copyright IBM Corp., 2006. All rights reserved.
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 The CSS uses the UCW to find the CUCBs and decides which is the best channel/control unit pair to use for the which is the best channel/control unit pair to use for the operation.operation.
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Introduction to the new mainframe
© Copyright IBM Corp., 2006. All rights reserved.
Mapping for access to devices (Cont...)
z/OSUCB
CUESCDESCD
Unitaddress '0A'
Device number
200A
ESCON/FICONI/O interface
Unit adress
UA=0A
1A
2A
8A
9A
ESCDESCD
ESCDESCD
ESCDESCD
CHANNELSUBSYSTEM
UCW
CU
CU
CU
subchannelnumber
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Introduction to the new mainframe
© Copyright IBM Corp., 2006. All rights reserved.
DASD Subsystem
FF00
FF01
FF02
FF03
20002001200220032004
200520062007
20082009
200A200B200C
200D200E
200F
CU
CU
disk drives
ESCON/FICON Directors
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.
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Introduction to the new mainframe
© Copyright IBM Corp., 2006. All rights reserved.
Redundant array of independent disk (RAID)
data 1data 2data 3data 4data 5data 6data 7data 8
data 1
data 5
data 2
data 3
data 4
data 6
data 7
data 8
RAID 5
party 4-7
party 3-6
party1-8
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.
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Introduction to the new mainframe
© Copyright IBM Corp., 2006. All rights reserved.
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...
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Introduction to the new mainframe
© Copyright IBM Corp., 2006. All rights reserved.
Multiple allegiance(MA)/Parallel access volume(PAV)
MA PAV
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Introduction to the new mainframe
© Copyright IBM Corp., 2006. All rights reserved.
Random access to data
RAID : First slow, as of next high-speed retrieval
Predictive loading : load the data into the CONTROL UNIT CACHE
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Introduction to the new mainframe
© Copyright IBM Corp., 2006. All rights reserved.
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
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Introduction to the new mainframe
© Copyright IBM Corp., 2006. All rights reserved.
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
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Introduction to the new mainframe
© Copyright IBM Corp., 2006. All rights reserved.
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
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Introduction to the new mainframe
© Copyright IBM Corp., 2006. All rights reserved.
Data placement and management
Performance
Space
Backup
Migration
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Introduction to the new mainframe
© Copyright IBM Corp., 2006. All rights reserved.
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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Introduction to the new mainframe
© Copyright IBM Corp., 2006. All rights reserved.
Key terms in this chapter
• Channel subsystem• CKD• Control block• Control Unit• DASD• Data Sharing
• DFSMS• FBA• Logical address• PAV• RAID