Introduction to z/OS

Introduction to z/OS

1. Intro to z/OS
Steve Warren
IBM
November 2020
Session 5AO

2. Introduction
•This presentation will cover (at the 50,000 footlevel) many different
areas (but not all) of z/OS
•Don’t be overwhelmed. There is a ton of material here. The purpose
of this session is to acquaint you with some of the major concepts of
z/OS
z/OS Concepts #CC 2

3. Agenda
Why Z Mattersand Why z/OS
Hardware/LPAR
z/OS Components
Software Stack
App Dev, App Exec and MgmtEnvs
DASD
Data Sets / Allocation
PDS & PDSE
VTOC & Catalogs
SMS
TSO/E
ISPF
z/OS UNIX/ISHELL/OMVS/Remote
Address Spaces & Modes
Storage & DAT
Batch Processing/JES/JCL
SDSF
Job Flow
System Log
IPL
Sysplex/GDPS
Serialization
Managing Workloads
z/OS Concepts #CC 3

4. 4
Why Z Matters?

5. Why Z Matters
z/OS Concepts #CC 5
Utilities Retail
Government
Financial
Travel
Healthcare
Automotive
Telecoms
Weather

6. Why Z Matters
Mainframes process 30 billion
business transactions per day
z/OS Concepts #CC 15
Mainframes process 1.3 million
CICS transactions. Every second. Every day.
Mainframes enable $6 trillion
in card payments annually
80 percent of the world’s corporate
data originates on mainframes
91 percent of CIOs said new customer-
facing apps are accessing the mainframe

7. Why z/OS?
z/OS Concepts #CC 16
•Ideally suited for processing large workloads for many concurrent users
•Highest security ratings for an OS
•Highest reliability
•Low TCO compared to other enterprise competitors
•Designed for:
•Serving 1000s of users concurrently
•I/O and numeric intensivecomputing
•Processing very large heterogeneous workloads
•Running mission critical applications securely

8. 17
Naming of OS

9. z/OS Lineage
•At the beginning there was:
•OS/360 (1966)
•Configuration options PCP, MFT and MVT
•OS/VS2 R1 (~1972)
•Retroactively renamed to SVS
•OS/VS2 R2 (~1974)
•Also called MVS
•MVS/370 (~1977)
•MVS/SP V1
•Optionally DFDS and DFEF
•MVS/XA (1983)
•MVS/SP V2 or V3 and MVS/DFP
•MVS/ESA (~1990)
•MVS/SP V4 or V5
•Either MVS/DFP or DFSMS/MVS
•OS/390 (1996)
•z/OS (2001)
z/OS Concepts #CC 18
Since 2001the name
has remainedz/OS
This is the longest
that it has been called
one name!
Since 2001the name
has remainedz/OS

10. 19
Hardware Context of
z/OS

11. IBM Z Server –the IBM z15
z/OS Concepts #CC 20

12. IBM Z Server –Multiple LPARs
z/OS Concepts #CC 21
CP, Memory, I/O
PR/SM™
LPAR LPAR LPAR LPAR LPAR LPAR LPAR
Support Element (SE)
Up to 85
LPARs can be
defined
Each LPAR can
be allocated
different
amounts of
resources (up to
16TB memory)

13. IBM Z Hardware and z/OS
z/OS Concepts #CC 22
Support Element (SE)
CP, Memory, I/O
PR/SM™
z/OS®
ICF
–
CFCC
z/VSE®
z/TPF
z/VM®
z/OS®
Linux on z Systems® Linux on z Systems®
Linux on z Systems® Linux on z Systems®
z/OS (a.k.a. Multiple Virtual
Storage -MVS)
Where we will be spending our
time

14. 23
z/OS Elements,
Features, and
Components

15. z/OS Concepts –Elements, Features,
Components
•z/OS is a collectionof elements
•Each element consists of a collection of modules (called components)
z/OS Concepts #CC 24
Examples:
IOS, RSM, GRS, Contents,
Allocation, Consoles, NIP,
Scheduler, SMF, BCPii, Logger

16. z/OS Concepts –Elements, Features,
Components
•z/OS is a collectionof elements
•Each element consists of a collection of modules (called components)
•Base elements are always included in z/OS
•BCP (Base Control Program)
•DFSMSdfp(Data Facility Storage Management Subsystem)
•Deliver essential operating system functions
z/OS Concepts #CC 25
Other Base Elements:
Communication Server, z/OSMF,
HLASM, TSO, ISPF, JES2,
Metal C Runtime Library

17. z/OS Concepts –Elements, Features,
Components
•z/OS is a collectionof elements
•Each element consists of a collection of modules (called components)
•Base elements are always included in z/OS
•BCP (Base Control Program)
•DFSMSdfp(Data Facility Storage Management Subsystem)
•Deliver essential operating system functions
•Optional features installed in addition to base elements
•Requested separately from base elements
•Can be priced orfree
z/OS Concepts #CC 26
Optional Features
Examples:
Security Server, SDSF,
XL C/C++, RMF, JES3,
DFSMShsm, DFSMSdss

18. 27
Software Stack

19. IBM z/OS Software Stack
z/OS Concepts #CC 28
z/OS®
Operating System
Middleware
Applications
Provides critical set of
system servicesmade
possible by the
z/Architecture
®
and
firmware

20. IBM z/OS Software Stack
z/OS Concepts #CC 29
z/OS®
Operating System
Middleware
Applications
Softwarethat is
neither operating
system code nor an
end-user application

21. IBM z/OS Software Stack
z/OS Concepts #CC 30
SAP is the registered trademark of SAP SE in Germany and in several other countries.
z/OS®
Operating System
Middleware
Applications
Db2
®
Data Base 2
CICS
®
Customer Information Control System
IMS™ Information Management System
WAS WebSphere
®
Application Server
IBM MQIBM Message Queuing
SAP
®
Systems, Applications and Products in Data
Processing
TSO/E Time Sharing Option/Extensions

22. IBM z/OS Software Stack
z/OS Concepts #CC 31
z/OS®
Operating System
Middleware
Applications Provideend-user
interface to product
solutions
ISPF Interactive System Productivity Facility
SA z/OSIBM System Automation for z/OS

23. 32
Application Development Environments,
Application Execution Environments and
z/OS Management Environments

24. Application Development Env
z/OS Concepts #CC 33
z/OS supports many programming languages as well as
modern IDEsand environments

25. Application Development Env
z/OS Concepts #CC 34
z/OS supports many programming languages as well as modern
IDEsand environments
•Assembler
•COBOL
•C/C++
•PL/I
•Fortran
•REXX
•JAVA
TM
•Python
•Node.js
•Scala

26. Application Development Env
z/OS Concepts #CC 35
Legacy interactive interface

27. Application Development Env
z/OS Concepts #CC 36
Legacy interactive interface
Integrated Development
Environment (IDE)

28. Application Development Env
z/OS Concepts #CC 37
Legacy interactive interface
Integrated Development
Environment (IDE)
Other Modern Application
Development Tools

29. Application Development Env
z/OS Concepts #CC 38

30. Application Execution Env
z/OS Concepts
#CC
39
Traditional z/OS
application environments,
including middleware
z/OS UNIX application
environment
z/OS Container Extensions
application environment
Java Virtual Machine
application environment

31. Management Environments
z/OS Concepts #CC 40
z/OS Management Facility (z/OSMF) provides modern interface
to help manage your z/OS systems

32. 41
DASD

33. IBM Speak –DASD
•DASD–Direct Access Storage Device
•Think “Hard Drive”
z/OS Concepts #CC 42

34. IBM Speak –DASD
•DASD–Direct Access Storage Device
•Think “Hard Drive”
•a.k.a. DASD Volume
•Volume needs a label
•Volume Serial Number (VOLSER)
•1 to 6 characters
z/OS Concepts #CC 43

35. 44
Data Sets

36. IBM Speak –Data Set
•Data set
•Think “File”
•Contains data in different structured formats
•Need to choose the format of data set and reserve
space (allocate dataset) prior to using for the first time
•Resides on DASD, Tape
•z/OS has types of data sets
•Legacy Data set
•Unix file
z/OS Concepts #CC 45
IBM prefers the
spelling “data set” to
“dataset”

37. IBM Speak –Data Set
z/OS Concepts #CC 46
DSORG=PS(Physically Sequential)
Data
Editingthe data set gives you all
the datain the data set

38. Directory
IBM Speak –Data Set
z/OS Concepts #CC 47
DSORG=PO(Partitioned)
DSORG=PS(Physically Sequential)
Data
Member 2 DataMember 1 Data Member 3 Data
The PDS contains a directoryto
locatethe members

39. PDS & PDSE
•PDSE data sets can be used in place of nearly all PDS data sets
•PDSE designed to address running out of space issues
•Compressionis not necessary
•PDSE directory expands to fit the members
z/OS Concepts #CC 48

40. IBM Speak –Data Set Name
•Data set name (DSN or DSName)
•Think “File Name”
z/OS Concepts #CC 49

41. IBM Speak –Data Set Name
•Data set name (DSN or DSName)
•Think “File Name”
•1 to 22 segments
•segments separated by a period
•each segment limited to 8 characters
z/OS Concepts #CC 50
FRED.ASSEMBLE.SOURCE

42. IBM Speak –Data Set Name
•Data set name (DSN or DSName)
•Think “File Name”
•1 to 22 segments
•segments separated by a period
•each segment limited to 8 characters
•Up to 44 characters (includes periods)
•High-level qualifier (HLQ) is typically your userid
z/OS Concepts #CC 51
FRED.ASSEMBLE.SOURCE
High-level
qualifier
(HLQ)
Low-level
qualifier

43. 52
Data Set
Allocation

44. IBM Speak –Data Set Allocation
•Data set allocation
•Think “Create Space” for a data set on disk
z/OS Concepts #CC 53

45. IBM Speak –Data Set Allocation
•Data set allocation
•Think “Create Space” for a data set on disk
•Need:
•Data set name
•VOLSER(i.e., the DASD volume) where the space should be
allocated
•Data set attributes(Size, RECFM, LRECL, BLKSZE, DSORG)
z/OS Concepts #CC 54

46. 55
VTOC and Catalogs

47. IBM Speak –VTOC & Catalogs
z/OS Concepts #CC 56
VOL100
FRED.ASSEMBLE.SOURCE
Allocate space for data set
FRED.ASSEMBLE.SOURCE
on volume VOL100
VOLSER

48. IBM Speak –VTOC & Catalogs
z/OS Concepts #CC 57
VOL100
FRED.ASSEMBLE.SOURCE
VTOC
DASD volume has a Volume
Table of Contents(VTOC) that
locates adata set on the
volume

49. IBM Speak –VTOC & Catalogs
z/OS Concepts #CC 58
VOL100
FRED.ASSEMBLE.SOURCE
VTOC
VOL002
SYS1.USERCAT
FRED.ASSEMBLE.SOURCE
is on VOL100
To simplify find the data set,
the name and location
information is placed in a
catalog

50. IBM Speak –VTOC & Catalogs
z/OS Concepts #CC 59
VOL100
FRED.ASSEMBLE.SOURCE
VTOC
VOL002
SYS1.USERCAT
FRED.ASSEMBLE.SOURCE
is on VOL100
There can be many catalogs
so how do we locate the
correct one?

51. IBM Speak –VTOC & Catalogs
z/OS Concepts #CC 60
VOL100
FRED.ASSEMBLE.SOURCE
VTOC
VOL001
SYS1.MSTRCAT
FRED.* data sets
cataloged in
SYS1.USERCAT on VOL002
VOL002
SYS1.USERCAT
FRED.ASSEMBLE.SOURCE
is on VOL100
We look in the “Master”
catalog(of which there is
only one)

52. IBM Speak –VTOC & Catalogs
z/OS Concepts #CC 61
VOL100
FRED.ASSEMBLE.SOURCE
VTOC
VOL001
SYS1.MSTRCAT
FRED.* data sets
cataloged in
SYS1.USERCAT on VOL002
VOL002
SYS1.USERCAT
FRED.ASSEMBLE.SOURCE
is on VOL100
The mastercatalog contains an HLQ of
FRED and indicates that all of Fred’s
data setsare cataloged in the user
catalognamed SYS1.USERCAT

53. IBM Speak –VTOC & Catalogs
z/OS Concepts #CC 62
VOL100
FRED.ASSEMBLE.SOURCE
VTOC
VOL001
SYS1.MSTRCAT
FRED.* data sets
cataloged in
SYS1.USERCAT on VOL002
VOL002
SYS1.USERCAT
FRED.ASSEMBLE.SOURCE
is on VOL100
Now we can tell z/OS to find
FRED.ASSEMBLE.SOURCE without
giving any more location information

54. 63
SMS

55. z/OS Concepts –SMS
•Data set management is tedious& error prone
z/OS Concepts #CC 64

56. z/OS Concepts –SMS
•Data set management is tedious& error prone
•IBM introduced SMS(System-Managed-Storage) to address this concern
z/OS Concepts #CC 65

57. z/OS Concepts –SMS
•SMS -automated approach to managingstorage resources
z/OS Concepts #CC 66

58. z/OS Concepts –SMS
•SMS -automated approach to managingstorage resources
•Uses software to manage
•data security
•data placement
•migration –move to tape
•backup
•recall –move from tape to DASD
•recovery –restore damaged data set
•deletion
•encryption
•compression
•And …
z/OS Concepts #CC 67

59. 68
TSO/E

60. Interacting with z/OS –TSO
•End users (sometimes tens of thousands of them) use the
system
•TSO/E (Time Sharing Option/Extensions) allows users to log on and
interactively share resources
•Supports limited set of basic commands
•Sometimes called using TSO in its “native mode”
z/OS Concepts #CC 69

61. Interacting with z/OS –TSO
•End users (sometimes tens of thousands of them) use the
system
•TSO/E (Time Sharing Option/Extensions) allows users to log on and
interactively share resources
•Supports limited set of basic commands
•Sometimes called using TSO in its “native mode”
z/OS Concepts #CC 70

62. Interacting with z/OS –TSO
z/OS Concepts #CC 71
You provide your userid
and password

63. Interacting with z/OS –ISPF
z/OS Concepts #CC 72
Because TSO/E
native mode
supports limited
functions, most
users go right to ISPF

64. 73
ISPF

65. Interacting with z/OS –ISPF
•ISPF(Interactive System Productivity Facility)
•Full panel application
•Panels are hierarchical
z/OS Concepts #CC 74

66. Interacting with z/OS –ISPF
•ISPF(Interactive System Productivity Facility)
•Full panel application
•Panels are hierarchical
•Navigatedvia keyboard
•F7 andF8 scroll backward andforward
•Enter (not right-ctrl) moves cursor to next input field
•Homemoves cursor to first input field
•ISPF use of Function Keys
•Provides text editorand browser
•Data set utilities
•Allocation
•Deletion
•Locating and Listing
•etc.
z/OS Concepts #CC 75

67. Interacting with z/OS –ISPF
z/OS Concepts #CC 76
Specifythe data set
name(or use wildcards)
that you want to display
and press Enter

68. Interacting with z/OS –ISPF
z/OS Concepts #CC 77
Side note:
To list the available
commands, enter a
slash “ /“

69. Interacting with z/OS –ISPF
z/OS Concepts #CC 78
Enter the number
of the function you
desire

70. Interacting with z/OS –ISPF
z/OS Concepts #CC 79
You writeyour
program!

71. 80
z/OS UNIX

72. Interacting with z/OS –UNIX
•z/OS UNIX a certified UNIX operating system by the Open Software
Foundation
•z/OS UNIX
®
provides another interactive way to access z/OS
•UNIX-compliant applications can be recompiled on z/OS unmodified and run
directly on z/OS
•Before we examine some UNIX functions, we need to understand the
z/OS UNIX file system
•In particular, the zFS (zSeries File System)
z/OS Concepts #CC 81
UNIX is a registered trademark of The Open Group

73. Interacting with z/OS –UNIX zFS
•Path name identifies a file
•Consistsof directorynames and a filename
•Up to 1023characters
•Directories and file name separatedbya forward-slash ( / )
/dir1/dir2/dir3/MyFile
z/OS Concepts #CC 82

74. Interacting with z/OS –UNIX zFS
•Path name identifies a file
•Consistsof directorynames and a filename
•Up to 1023characters
•Directories and file name separatedbya forward-slash ( / )
/dir1/dir2/dir3/MyFile
•Names arecase sensitive
z/OS Concepts #CC 83

75. Interacting with z/OS –UNIX
•z/OS UNIX provides three main environments
•ISHELL & z/OS UNIX Directory List Utility
•ISPF panel interfaces to z/OS UNIX System Services
•Good for users familiar with TSO and ISPF
z/OS Concepts #CC 85

76. Interacting with z/OS –UNIX
•z/OS UNIX provides three main environments
•ISHELL & z/OS UNIX Directory List Utility
•ISPF panel interfaces to z/OS UNIX System Services
•Good for users familiar with TSO and ISPF
•OMVS
•The z/OS UNIX shell
•Users of current UNIX systems find the z/OS UNIX shell environment familiar
z/OS Concepts #CC 86

77. Interacting with z/OS –UNIX
•z/OS UNIX provides three main environments
•ISHELL & z/OS UNIX Directory List Utility
•ISPF panel interfaces to z/OS UNIX System Services
•Good for users familiar with TSO and ISPF
•OMVS
•The z/OS UNIX shell
•Users of current UNIX systems find the z/OS UNIX shell environment familiar
•Remote UNIX interfaces
•z/OS UNIX can be accessed thru standard UNIX interfaces remotely
•Telnet, SSH, NFS
z/OS Concepts #CC 87

78. 88
ISHELL & z/OS UNIX
Directory List Utility

79. Interacting with z/OS –ISHELL
z/OS Concepts #CC 89
This panel is
tailorable so your
data may be
displayed differently

80. Interacting with z/OS –ISHELL
z/OS Concepts #CC 90

81. Interacting with z/OS –z/OS UNIX Directory List Utility
z/OS Concepts #CC 91
ISPF Option 3.17

82. Interacting with z/OS –z/OS UNIX Directory List Utility
z/OS Concepts #CC 92

83. 93
OMVS

84. Interacting with z/OS –OMVS
z/OS Concepts #CC 94
Here we have
our helowrld
file

85. Interacting with z/OS –OMVS
z/OS Concepts #CC 95
We use the
oeditcommand
to edit the file

86. Interacting with z/OS –OMVS
z/OS Concepts #CC 96

87. 97
Remote UNIX
Interfaces

88. Interacting with z/OS -Telnet
z/OS Concepts #CC 98
•Remote command execution
•Connection may be encrypted
•Automatically converts EBCDIC on the mainframe side to ASCII on the
user side
•Telnet client is needed
•Userid/password of valid z/OS useridrequired

89. Interacting with z/OS –SSH
z/OS Concepts #CC 99
•Remote command execution
•Connection is encrypted
•Automatically converts EBCDIC on the mainframe side to ASCII on the
user side
•SSH client is needed
•Public/private encryption key pair needs to be generated
•No userid/password needs to be specified
•Public key needs to be stored on z/OS

90. Interacting with z/OS –SSH
z/OS Concepts #CC 100

91. Interacting with z/OS –NFS
z/OS Concepts #CC 101
•Network file system
•Acts as a file server to remote systems
•Client sees data sets or files as if they are local resources
•Access to both traditional z/OS data sets and z/OS UNIX files
•Connection may be encrypted
•Automatically converts EBCDIC on the mainframe side to ASCII on the
user side
•NFS client is needed
•mvslogincommand required to logon to z/OS
•mount command used to make a connection between a drive letter of
local system and z/OS data sets or z/OS UNIX directories

92. Interacting with z/OS –NFS
z/OS Concepts #CC 102
c:\znfs-client-utils>mvslogin mvshostsmith
GFSA968I UNIX uid=502/gid=1000 for user JSmithobtained
from local passwd file.
Password required
GFSA973A Enter MVS password for SMITH: ********
GFSA955I SMITH logged in ok.
c:\znfs-client-utils>mount \\mvshost\mvs\smith J:
J: is now successfully connected to \\mvshost\mvs\smith
The command completed successfully.
c:\znfs-client-utils> J:
j:\>

93. 103
Address Spaces

94. z/OS Address Spaces
z/OS Concepts #CC 104
z/OS®
z/OS is structuredaround address spaces
Address spaces are ranges of addressesin
virtual storage
Each user gets an address space containing
the same range of addresses

95. z/OS Address Spaces
z/OS Concepts #CC 105
z/OS®
z/OS is structuredaround address spaces
Address spaces are ranges of addressesin
virtual storage
Each user gets an address space containing
the same range of addresses

96. z/OS Address Spaces
z/OS Concepts #CC 106
z/OS®
z/OS is structuredaround address spaces
Address spaces are ranges of addressesin
virtual storage
Each user gets an address space containing
the same range of addresses

97. z/OS Address Spaces
z/OS Concepts #CC 107
Wilma
0
16 MB
2 GB
16 EB
BarneyFred
Each user’s
address space has
the same range of
addresses
0 –16 EB
(exabyte)
1 EB = 1 billion
gigabytes (10
18
)

98. z/OS Address Spaces
z/OS Concepts #CC 108
PCAuth
RASP
Master
Besides an
address space for
each user, z/OS
creates address
spaces (~35) for
some of its
internal
components
Trace
DumpSrv
XCFAS
GRS

99. z/OS Address Spaces
z/OS Concepts #CC 109
SDSFAUX
VTAM
SDSF
TCAS
TCPIP
XCFAS
GRS
PCAuth
RASP
Master
Trace
DumpSrv
Then address
spaces for
middleware
and
applications
are created

100. 111
What makes up an
Address Space?

101. What Makes Up an Address Space?
z/OS Concepts #CC 112
Prefixed Save Area (PSA)
System code and data
common to all address spaces
z/OS system data for the address space
Not available to z/OS. Used by JAVA™
Shared and common data areas
~
~~
~
2 GB
"The
Bar"
16 MB
“The
Line”
16 EB
0
z/OS has storage rangesthat
contain code/data that is
common to alladdress spaces

102. What Makes Up an Address Space?
z/OS Concepts #CC 113
Prefixed Save Area (PSA)
System code and data
common to all address spaces
z/OS system data for the address space
Not available to z/OS. Used by JAVA™
Shared and common data areas
~
~~
~
2 GB
"The
Bar"
16 MB
“The
Line”
16 EB
0
Private Area
Private Area
Private Area
Private Area
What is left is
the “Private
Area” that is
available for
your use

103. What Makes Up an Address Space?
z/OS Concepts #CC 114
~
~~
~
2 GB
"The
Bar"
16 MB
“The
Line”
16 EB
0
But how much
can your
program see
(i.e., address)?

104. 115
Addressing Modes

105. Addressing Modes
z/OS Concepts #CC 116
16 MB
0
An address space size
is limited to the
amount of memory
that can be addressed
In 1977, an address
space was limited to
16 MB

106. Addressing Modes
z/OS Concepts #CC 117
2 GB
0
In 1981, an address
space size increased to
a sizeof
2 GB

107. Addressing Modes
z/OS Concepts #CC 118
2 GB
16 MB
“The
Line”
0
The concept of
“The Line” was
introduced

108. Addressing Modes
z/OS Concepts #CC 119
2 GB
16 MB
“The
Line”
0
MyPgm24
Programs not changed to
support 31-bit addressing
had to run and could only
access datathat was
“Below the line”
Data

109. Addressing Modes
z/OS Concepts #CC 120
2 GB
16 MB
“The
Line”
0
MyPgm24
MyPgm31
Programs changed to
support 31-bit addressing
could run and could also
access datathat was
“Above the line”
Data
Data

110. Addressing Modes
z/OS Concepts #CC 121
2 GB
16 MB
“The
Line”
0
MyPgm24
MyPgm31
Needed a way to indicate
which addressing mode the
program supported
Programs now have to
specify:
AMODE 24 or
AMODE 31
Data
Data

111. Addressing Modes
z/OS Concepts #CC 122
2 GB
16 MB
“The
Line”
0
MyPgm24
MyPgm31
Since AMODE 31 programs
could run (i.e., be loaded)
above or below the line, a
way was needed to request
where the program should
reside
Data
Data

112. Addressing Modes
z/OS Concepts #CC 123
2 GB
16 MB
“The
Line”
0
MyPgm24
MyPgm31
Programs now have to
specify a residency mode:
RMODE 24 or
RMODE 31
so z/OS knows where to
loadthe program
Data
Data

113. Addressing Modes
z/OS Concepts #CC 124
2 GB
16 MB
“The
Line”
0
MyPgm24
MyPgm31
AMODE 31
RMODE 31
Data
Data
AMODE 24
RMODE 24

114. Addressing Modes
z/OS Concepts #CC 125
2 GB
16 MB
“The
Line”
0
MyPgm31Data
Data
AMODE 31
RMODE 24
This request is
also possible

115. Addressing Modes
z/OS Concepts #CC 126
2 GB
16 MB
“The
Line”
0
Data
AMODE 24
RMODE 31
This request is impossible!
Brancheswithin MyPgm24 would
fail since the target location is in 31-
bit storagebut the address being
used is a 24-bit address
MyPgm24

116. Addressing Modes
z/OS Concepts #CC 127
~
~~
~
16 MB
“The
Line”
16 EB
0
In 2000, an address
space size in creased
to 64-bitor
16 EB

117. Addressing Modes
z/OS Concepts #CC 128
~
~~
~
2 GB
"The
Bar"
16 MB
“The
Line”
16 EB
0
The concept of
“The Bar” was
introduced

118. Addressing Modes
z/OS Concepts #CC 129
~
~~
~
2 GB
"The
Bar"
16 MB
“The
Line”
16 EB
0
AMODE 64 is introduced
and datacan now be
accessed “Above the
Bar”
While RMODE 64 is
supported by
z/Architecture, z/OS does
not support it
MyPgm6424
MyPgm6431
Data
Data
Data

119. Addressing Modes
z/OS Concepts #CC 130
~
~~
~
2 GB
"The
Bar"
16 MB
“The
Line”
16 EB
0
MyPgm6424
MyPgm6431
Data
Data
With z/OS V2R3 and
beyond, z/OS supports
RMODE 64
With restrictions
Programs will be loaded
“Above the Bar”
MyPgm6464
Data

120. 131
Storage

121. Storage
•Programs are written to utilizea given amount of memory.
z/OS Concepts #CC 132

122. Storage
•Programs are written to utilizea given amount of memory.
•The amount of memoryrequired by allthe running tasksis usually
much greaterthan the amount of real storageavailable.
z/OS Concepts #CC 133

123. Storage
•Programs are written to utilizea given amount of memory.
•The amount of memoryrequired by allthe running tasksis usually
much greaterthan the amount of real storageavailable.
•This is facilitated by the use ofvirtual storage.
z/OS Concepts #CC 134

124. Storage
z/OS Concepts #CC 135
When a task is active, its memory
is brought intoreal storage.

125. Storage
z/OS Concepts #CC 136
The rest can stayin auxiliary
storage, enabling the remaining
real storage to be used for other
programs.

126. Storage
•Virtualstorage is divided into 4KBpieces called pages.
•Realstorage is divided into 4KBpieces called frames.
•Auxiliarystorage is divided into 4KBpieces called slots.
z/OS Concepts #CC 137

127. 138
Dynamic Address
Translation (DAT)

128. Address Translation
•When a program is running, the processor must be able to
locateits virtual pagesin real storage.
z/OS Concepts #CC 139

129. Address Translation
•When a program is running, the processor must be able to
locateits virtual pagesin real storage.
•Address translation is the process that enables a processor
to convert virtual addresses into real addresses.
z/OS Concepts #CC 140

130. 141
Batch Processing

131. Batch Processing
•z/OS is also ideal for batch jobs
•Workloadsthat run inbackground
•Little or no human interaction
z/OS Concepts #CC 142

132. Batch Processing
•Many customer core applications, such as payroll, are performed
through batch processing (jobs)
•Jobs run without end user interaction
•Run as resources permit
•JCL(Job Control Language) is used to control the operationof each
job
z/OS Concepts #CC 143

133. Batch Processing
z/OS Concepts #CC 144
Example
of JCL

134. Batch Processing
z/OS Concepts #CC 145
JCL statements
start with a // in
column 1

135. Batch Processing
•An initiator(system program)
•Processes JCL
•Creates environment in an address space
•Runs the job in that address space
z/OS Concepts #CC 146

136. Batch Processing
•Managementof jobs & resources are sharedbetween z/OS and JES
(Job Entry Subsystem)
z/OS Concepts #CC 147

137. Batch Processing
•Managementof jobs & resources sharedbetween z/OS and JES
(Job Entry Subsystem)
•JES
•Receivesjobs into system
•Queuejobs waiting to be executed
•Manages priority
•Schedulesfor processing
•Controls outputprocessing
z/OS Concepts #CC 148

138. 149
Job Flow

139. Job Flow
z/OS Concepts #CC 150
Typical
Job Flow

140. 151
SDSF

141. Batch Processing –SDSF
z/OS Concepts #CC 152
We want to see the output
status of our job
Option “ST” is used

142. Batch Processing –SDSF
z/OS Concepts #CC 153
This is the job
we just ran

143. Batch Processing –SDSF
z/OS Concepts #CC 154
To see the
output, type “S”
for select

144. Batch Processing –SDSF
z/OS Concepts #CC 155
Messagesissued by
z/OS on behalf of
your job are
displayed

145. 156
System Log

146. z/OS Concepts –SYSLOG
•What is the System Log?
•Better known as SYSLOG
•a.k.a. Hardcopy Log (at one time this was a printer)
•Chronologicallisting of messagesabout z/OS system activity and other major
middleware software products
•Issued system commands and their responses
•When an unexpectedsystem problemoccurs, the SYSLOG is the first
place to look to gather information about the problem
z/OS Concepts #CC 157

147. z/OS Concepts –SYSLOG
z/OS Concepts #CC 158
Message ID of a message
Every message starts with an ID
(up to 10 characters)
Enables you to look up message in
documentation

148. 159
IPL and System
Address Space
Initialization

149. IBM Speak -IPL
•IPL–Initial Program Load
•Think “Boot the System”
•Starting z/OS
z/OS Concepts #CC 160

150. IBM Speak -IPL
z/OS Concepts #CC 161
Use a special console
connected to the internal
network of mainframe boxes
(HMC) and
activate the “Load Profile”
Profile contains DASD
device number to IPL

151. IBM Speak -IPL
z/OS Concepts #CC 162
HMC
“current”
screen
image

152. IBM Speak -IPL
z/OS Concepts #CC 163
Load Profile
Device address
to IPL
0980
0CE3W1

153. IBM Speak -IPL
z/OS Concepts #CC 164
IPL processed in
phases
Each phase
builds on the
previous

154. IBM Speak -IPL
z/OS Concepts #CC 165
0980
SYSRS1
To “Boot” or “IPL”
z/OS, the device
number of the
SYSRES(system
residence volume)
is specified

155. IBM Speak -IPL
z/OS Concepts #CC 166
JES2
RACF
RESOLVER
LLA
VLF
HZR
JES2AUX
MSI–several z/OS
component address
spaces created
After MSI, queued
STARTcommands are
processed
Additional z/OS
component address
spaces are created

156. IBM Speak -IPL
Important address spaces started at Master Scheduler Initialization
time (MSI):
•SMF (System Management Facility)
z/OS Concepts #CC 167
Collector of system and job-
related informationused for:
billing users, reporting reliability,
analyzing the configuration,
evaluating activity, profiling system
resource use, maintaining system
security.

157. IBM Speak -IPL
Important address spaces started at Master Scheduler Initialization
time (MSI):
•SMF (System Management Facility)
•System Logger
z/OS Concepts #CC 168
A set of services that allow an
application to write, browse, and
delete log data. Designed to
merge datafrom multiple
instances of an application,
including merging data from
different systems across a sysplex.

158. IBM Speak -IPL
Important address spaces started at Master Scheduler Initialization
time (MSI):
•SMF (System Management Facility)
•System Logger
•BCPii(Base Control Program internal interface)
z/OS Concepts #CC 169
A set of services that allow
special z/OS applications a way of
programmatically controlling the
mainframe hardware
configuration

159. IBM Speak -IPL
Important started address spaces
•JES(Job Entry Subsystem a.k.a. JES2 or JES3)
z/OS Concepts #CC 170
Receives jobs, schedules them for
processingand handles their output

160. IBM Speak -IPL
Important started address spaces
•JES(Job Entry Subsystem a.k.a. JES2 or JES3)
•RACF® (Resource Access Control Facility a.k.a. z/OS Security Server)
z/OS Concepts #CC 171
Securityprogram used to protect
resources

161. IBM Speak -IPL
Important started address spaces
•JES(Job Entry Subsystem a.k.a. JES2 or JES3)
•RACF® (Resource Access Control Facility a.k.a. z/OS Security Server)
•ICSF (Integrated Cryptographic Service Facility)
z/OS Concepts #CC 172
Provides the z/OS Cryptographyinterfaces
to applications: Enciphering, Deciphering,
Hashing, andGenerating/verifying
digital signatures. Implements this via
both crypto hardware and software.

162. IBM Speak -IPL
Important started address spaces
•JES(Job Entry Subsystem a.k.a. JES2 or JES3)
•RACF® (Resource Access Control Facility a.k.a. z/OS Security Server)
•ICSF (Integrated Cryptographic Service Facility)
•VTAM® (Virtual Telecommunications Access Method a.k.a. z/OS Communications Server)
z/OS Concepts #CC 173
Implements SNA(Systems Network
Architecture)with API(Application Program
Interface)for communicatingwith devices
and programs

163. IBM Speak -IPL
Important started address spaces
•JES(Job Entry Subsystem a.k.a. JES2 or JES3)
•RACF® (Resource Access Control Facility a.k.a. z/OS Security Server)
•ICSF (Integrated Cryptographic Service Facility)
•VTAM® (Virtual Telecommunications Access Method a.k.a. z/OS Communications Server)
•TCAS (Terminal Control Address Space)
z/OS Concepts #CC 174
Communication interface for
TSO/E(Time Sharing
Option/Extensions)

164. IBM Speak -IPL
Important started address spaces
•JES(Job Entry Subsystem a.k.a. JES2 or JES3)
•RACF® (Resource Access Control Facility a.k.a. z/OS Security Server)
•ICSF (Integrated Cryptographic Service Facility)
•VTAM® (Virtual Telecommunications Access Method a.k.a. z/OS Communications Server)
•TCAS (Terminal Control Address Space)
•TCP/IP (Transmission Control Protocol/Internet Protocol a.k.a. z/OS Communications
Server: IP)
z/OS Concepts #CC 175
Networking protocolsfor computer
communications

165. IBM Speak -IPL
Important started address spaces
•JES(Job Entry Subsystem a.k.a. JES2 or JES3)
•RACF® (Resource Access Control Facility a.k.a. z/OS Security Server)
•VTAM® (Virtual Telecommunications Access Method a.k.a. z/OS Communications Server)
•TCAS (Terminal Control Address Space)
•TCP/IP (Transmission Control Protocol/Internet Protocol a.k.a. z/OS Communications
Server: IP)
z/OS Concepts #CC 176
Once TCP/IP is initialized,
the IPLis considered
complete

166. IBM Speak -IPL
•Of course there is still more work to be done
•Middlewareand applicationproductslike the following need to be
started:
•SA z/OS(System Automation for z/OS)
•DB2
®
(Data Base 2)
•CICS
®
Transaction Server for z/OS (Customer Information Control System)
•IMS
™
(Information Management System)
•WAS (WebSphere
®
Application Server)
z/OS Concepts #CC 177

167. 178
Sysplex

168. IBM Speak –Parallel Sysplex
•A sysplexis
•A collectionof z/OS systemsthat cooperate
•A Parallel Sysplex
•Is a sysplex that uses multisystem data-sharing technology
•Allows direct, concurrent read/write access to shared data fromall systems
without impacting performanceor data integrity
•Workrequeststhat are associated with a single workload
•Can be dynamically distributed for parallel execution on systems
•Based on availableprocessor capacity
•
z/OS Concepts #CC 179

169. IBM Speak –Parallel Sysplex
•In many ways a Parallel Sysplex appears as a singlelarge system
•The collection of z/OS systems cooperateto:
•Process workloads
•Provide higher availability
•Provide easier systems management
•Provide improved growth
z/OS Concepts #CC 180

170. Parallel Sysplex
z/OS Concepts #CC 181
This sysplexconsists of two z/OS
images, each on their own CPC

171. Parallel Sysplex
z/OS Concepts #CC 182
The z/OS
componentsthat
manage the
sysplex are:
XCF(cross system
coupling facility)
XES(cross-system
extended services)

172. Parallel Sysplex
z/OS Concepts #CC 183
XCFallows authorized programs on one
system to communicate with programs on
the same system or on other systems

173. Parallel Sysplex (7 of 13)
z/OS Concepts #CC 184
XES enables applicationsand subsystemsto
take advantageof the coupling facility

174. Parallel Sysplex
z/OS Concepts #CC 185
CF (Coupling Facility) provides:
•Data sharing across the systems in a sysplex
•Maintaining the integrity and consistency of
shared data
•Maintaining the availabilityof a sysplex

175. Parallel Sysplex
z/OS Concepts #CC 186
STP(Server Time Protocol) is required
to synchronize the TOD (time-of-day)
clocks for systems in a sysplex

176. Parallel Sysplex
z/OS Concepts #CC 187
Shared CDS(Couple Data
Sets) records status
information for the sysplex

177. Parallel Sysplex
z/OS Concepts #CC 188
Applications written to take advantage of a
parallel sysplex can have multiple
instancesrunning on any/all z/OS images
Data accessiblefrom all images

178. Parallel Sysplex
z/OS Concepts #CC 189
Application is still
availableif a failure in
one image/CPCoccurs

179. 190
Serialization

180. z/OS Concepts –Serialization
•Customers using z/OS may runs many concurrent programsand
many threads of the same program simultaneously.
•Thinkcredit card transactions!
z/OS Concepts #CC 191

181. z/OS Concepts –Serialization
•Customers using z/OS may runs many concurrent programsand
many threads of the same program simultaneously.
•Think credit card transactions!
•What if these programs need to update resources at the same time?
z/OS Concepts #CC 192

182. z/OS Concepts –Serialization
•Customers using z/OS may runs many concurrent programsand
many threads of the same program simultaneously.
•Think credit card transactions!
•What if these programs need to update resources at the same time?
•Data sets
•Virtual resources
•Lists
•Queues
•Data areas (control blocks)
z/OS Concepts #CC 193

183. z/OS Concepts –Serialization
•Customers using z/OS may runs many concurrent programsand
many threads of the same program simultaneously.
•Think credit card transactions!
•What if these programs need to update resources at the same time?
•Data sets
•Virtual resources
•Lists
•Queues
•Data areas (control blocks)
•How do we ensure data integrity and fair access to these resources?
z/OS Concepts #CC 194

184. z/OS Concepts –Serialization
•Global Resource Serialization (GRS) is the z/OS component designed
to protect the integrity of resources in a multitasking, multi-host
environment
z/OS Concepts #CC 195

185. z/OS Concepts –Serialization
•Global Resource Serialization (GRS) is the z/OS element designed to
protect the integrity of resources in a multitasking, multi-host
environment
•Coordinates access to resources used by more than one program
z/OS Concepts #CC 196

186. z/OS Concepts –Serialization
•Global Resource Serialization (GRS) is the z/OS element designed
to protect the integrity of resources in a multitasking, multi-host
environment
•Coordinates access to resources used by more than one program
•Uses ENQs andLatches to scope resources at various levels:
•STEP –synchronize within a single address space
•SYSTEM –synchronize single system apps
•SYSTEMS –synchronize multisystem apps
•SYSPLEX –synchronize across a sysplex
•Custom (Latches) –synchronize within a multitasking, or multi-threaded
application
z/OS Concepts #CC 197

187. z/OS Concepts –Serialization
•Program obtains ENQ orLatch before reading or updating
protected resource
z/OS Concepts #CC 198

188. z/OS Concepts –Serialization
•Program obtains ENQ or Latch before updating protected
resource
•Determines if it should be exclusive (write access) or
shared (read/only access)
z/OS Concepts #CC 199

189. 200
Managing Workloads

190. z/OS Concepts –Managing Workloads
•One of the strengths of the IBM Z platform and the z/OS operating
system is the ability to run multiple workloads at the same time
within one z/OS image or across multiple images.
z/OS Concepts #CC 201

191. z/OS Concepts –Managing Workloads
•One of the strengths of the IBM Z platform and the z/OS operating
system is the ability to run multiple workloads at the same time
within one z/OS image or across multiple images.
•z/OS needs to:
•Prioritize work
•Use the installation resources as efficiently as possible
•Maintain the highest possible throughput
•Achieve the best possible system responsiveness.
z/OS Concepts #CC 202

192. z/OS Concepts –Managing Workloads
•One of the strengths of the IBM Z platform and the z/OS operating
system is the ability to run multiple workloads at the same time
within one z/OS image or across multiple images.
•z/OS needs to:
•Prioritize work
•Use the installation resources as efficiently as possible
•Maintain the highest possible throughput
•Achieve the best possible system responsiveness.
•Dynamic workload management is accomplished through the
Workload Management (WLM)component of the z/OS operating
system
z/OS Concepts #CC 203

193. z/OS Concepts –Managing Workloads
•WLM allows a customer to define performance goalsand assign a
business importance to each goal.
z/OS Concepts #CC 204

194. z/OS Concepts –Managing Workloads
•WLM allows a customer to define performance goals and assign a
business importance to each goal.
•Goals are defined in business terms, and the system decides how
much resource, such as CPUand storage, should be given to the work
to meet its goal.
z/OS Concepts #CC 205

195. z/OS Concepts –Managing Workloads
•WLMalgorithms use the service definition information and internal
monitoring feedbackto check how well they are doing in meeting the
goals.
•Algorithms periodically adjust the allocation of resource as the workload level
changes.
z/OS Concepts #CC 206

196. z/OS Concepts –Managing Workloads
•WLMalgorithms use the service definition information and internal
monitoring feedbackto check how well they are doing in meeting the
goals.
•Algorithms periodically adjust the allocation of resource as the workload level
changes.
•For each system, WLM manages the system resources.
•Coordinates and shares performance information across the
sysplex.
•How well it manages one system is based on how well the other systems are also doing
in meeting the goals. If there is contention for resources,itmakes the appropriate trade-
offs based on the importance of the work and how well the goals are being met.
z/OS Concepts #CC 207

197. z/OS Concepts –Managing Workloads
•WLM can dynamically start and stop server address spaces to
process work from application environments.
•On a single system or across the sysplex
•Batch initiators can be managed
•Can dynamically manage the number of batch initiators for one or more job classes to
meet the performance goals of the work.
z/OS Concepts #CC 208

198. z/OS Concepts –Managing Workloads
•WLM can dynamically start and stop server address spaces to
process work from application environments.
•On a single system or across the sysplex
•Batch initiators can be managed
•Can dynamically manage the number of batch initiators for one or more job classes to meet
the performance goals of the work.
•WLM also collects real-time performance data anddelay monitoring.
•Available for performance monitors and reporters for integration into detailed
reports.
z/OS Concepts #CC 209

199. Please submit your session feedback!
•Do it online at http://conferences.gse.org.uk/2020/feedback/nn
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