Mainframe

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Mainframe
What is the mainframe?
Mainframe computers are computers used primarily by large organizations for
critical applications, bulk data processing such as census, industry and consumer
statistics, enterprise resource planning, and transaction processing.
Who use it?
Operations support: is the first point of contact when customers experience
problems with the mainframe. They must be able to resolve the problem or quickly
identify the people that can.
Computer operator: is responsible for monitoring the mainframe system,
resolving and reporting system related problems, ensure mainframe batch and
online processing is carried out per Service Level Agreements.
Production controller: schedules ongoing and on-demand job activity on the
mainframe and maintains procedures and standards associated with processing.
Application programmer: is responsible for designing, coding, testing,
implementing and supporting application software in a wide area of programming
environments (Cobol, c++, C, Java, CICS)
System programmer: responsible for the analysis, development, modification,
installation, testing and maintenance of the mainframe and middleware operating
systems software.
Capacity/performance analyst: the capacity specialist identifies future business
growth trends and reports on capacity requirements. The performance analyst is
responsible for the health of system and the reporting and analysis of system
performance data.
Database administrator: designs, implements and administrates the
organization’s database platforms.
Data center manager: has responsibility for the mainframe and network services
provided and handles contacts and Service Level Agreements associated with
support.
Chief information officer: incorporates the organization’s strategies along with
industry knowledge to determine the direction of IT.

Operating system:

z/VM (Virtual Machine): is an operating system that
enables organizations to run multiple operating systems on
a single machine. If required, z/VM can also be used as a
stand-alone operating system.
z/VSE: is an operating system which is commonly used with
smaller mainframes, provides organizations with a comparatively less complex
batch and transaction processing framework.
z/TPF (Transaction Processing Facility): is a specialized operating system that
is suited to organizations such as major airlines, credit card processors. z/TPF can
utilize multiple mainframes to handle tens of thousands of transactions while
providing uninterrupted availability.
z/OS is the premier IBM operating system and is direct descendant of the OS
operating systems. The z/OS operating system provides organizations with a reliable
platform that can handle thousands of programs and logged-in users concurrently.
z/OS characteristics:
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-

-

-

Security: prevents users from accessing or changing data residing on the
system if they do not have the authority.
Processing work: manages is own workload balancing and can handle
large numbers of concurrently running jobs without affecting the integrity
of data.
Recoverability: recovery is built into various levels of the system
minimizing the need for any unplanned system restarts. As each job is
processed in its own address space, if a problem occurs with that job it
won’t affect other system activities.
Managing Hardware: z/OS manages and enables sharing of a wide range
and number of hardware devices that can be found within the mainframe
environment: disk drivers, automated tape libraries, printers and network
terminals.
Communication: communicates via a console with personnel such as
operators, and displays information such as system status, problem
message, job flow progress and hardware availability.

Hardware components:
Processors:

CP: Acronym for central processor, which can be used to process workloads for
z/OS, Linux, z/ VM, Coupling Facility Control Code (CFCC), and TPF operating
systems.
System assistance processor(SAP): Responsible for running
internal microcode, primary to control the I/O subsystem.
IFL: Integrated Facility for Linux, is dedicated to running the Linux
operating system and is just a regular processor that couple of z/OS
related instructions disabled.

zAAP: Z system Application Assist Processor, runs dedicated Java
workloads under z/OS. This processors are regular processors with
several z/OS functions disabled.
zIIP: Z system Integrated Information Processor, is specially configured
for database(DB2) processing offers users a cheap alternative to the
fully configured processor.
ICF: Integrated Coupling Facility, enables multiple IBM mainframes to
share cache, update and balance data access across systems
Spares: Not configured processors installed and referenced only if the
system detects a falling central processor (takes on the workload on
the filed one).
Capacity on Demand: Allows the customer to initiate a permanent
increase in processing capacity.
Real storage:
Real storage is also referred to as processor storage, central storage or
real memory. For a program to be able to run, the program’s
instructions and data must both reside in real storage.
Auxiliary storage is referred as paging storage because as program
instructions and data are required for processing, they are moved or
paged from auxiliary storage to real storage.
Channel subsystem:
The mainframe, to send data such as DASD, printers, tapes and
cartridges, uses the channel subsystem.

LPAR
Logical partition:
1. (AS/400) A subset of a single iSeries system that contains resources
(processors, memory, and input/output devices). A logical partition operates as an
independent system. If hardware requirements are met, multiple logical partitions
can exist within a system.
2. (MVS) A division of processor resources (as determined by PR/SM) designated
for the running of an operating system.

The z/OS operating system contains the z/OS Communication Server, which has the
following three components:
SNA protocol stack, which is part of the VTAM (Virtual Telecommunication
Access Method):
1. Systems Network Architecture. The IBM architecture for controlling,
configuring, and transmitting data through networks.
2. In IBM networks, the description of the layered logical structure,
formats, protocols, and operational sequences that are used for
transmitting information units through networks, as well as controlling
the configuration and operation of networks.
TCP/IP protocol stack
1. Transmission Control Protocol/Internet Protocol. The Internet's
communication protocol.
2. A set of communications protocols that support peer-to-peer
connectivity functions for both local and wide area networks.
3. The primary communications protocol that is used on the Internet.
TCP/IP could also be used on an internal network.
CSM (Communication Storage Manager) that provides shared I/O data flow
involved in the communication process.

sysplex
A system complex. A group of MVS systems working in combination to process a workload.
Sysplex Timer

A device used to synchronize the time-of-day clocks of the processors in a sysplex.
How data is processed:
-

Online: requires human interaction
In batch (a batch job is creating a report using database records)

Common used transaction processing systems:
CICS:
1. Customer Information Control System - a family of IBM products that
manage online transactions.
2. An IBM licensed program that enables transactions entered at remote
workstations to be processed concurrently by user written application
programs. The licensed program includes functions for building, using, and
maintaining databases, and for communicating with CICS programs on other
operating systems.
IMS:
Information Management System: A family of IBM products that manage
online applications and hierarchical databases.
WebSphere Application Server for z/OS
Z/OSMF ( z/OS Management Facility): is a tool with a GUI interface, wizard and drill
down capabilities to make previously arduous system-related task simpler and less
prone to human error.

z/OSMF WLM ( z/OSMF Workload Manager) component controls the access to system
resources through work related goals and priorities, which it stores in service
definitions.
ISPF: is a user interface that allows those with authority, to interact with the z/OS
system itself. This option allows you to perform all the usual ISPF tasks as well as
being able to invoke SDSF and HCD.

Identify the Different Methods of Storing and accessing Mainframe data:
Mainframe data is stored in a file, as in a database file, or in a data set which is a
term used to describe an area of space occupied by a collection of related data.
Database file: contains a record of each customer and consists of a number of fields
such as customer name, address, accounts, transaction history and so on.
Sequential data set: is the simplest data structure of the z/OS system and consists
of one or more records stored in physical order and processed in sequence.
Partitioned data set: contains individual members, which in turn contain sequential
data. The benefit of this structure is that members do not need to contain a related
data as is the case with sequential data set.
VSAM data set: are useful when individual records from the data set can be selected
for processing. There are several different VSAM data set types depending on the
type of data that needs to be stored and how it will be processed.
Existing data sets and their attributes is stored in a catalog so that the system can
quickly identify whether data exists and where it is stored.
The main catalog is called Master catalog and contains entries for both data sets
and sub catalogs, which are called user catalogs.
VTOC(Volume table of contents):keeps track of data sets on individual DASD.
In today’s z/OS system, DFSMS is commonly used to automate data allocation and
the deletion, placement, backup, and recovery of data sets.
DFSMSdfp: comes with the z/OS and allows you to create storage policies that
are invoked when new data is created. These policies usually define the
attributes of a data set and where it will be placed.
DFSMSdss: is an optional component that can perform backup at data set and
volume level and allows copying or moving of data to other devices.
DFSMShsm: is an optional component that manages DASD storage by moving
less important or less accessed data to cheaper and usually slower mediums.
Can also be used to backup data.

DFSMSrmm: is an optional component used to manage removable media
devices such as tape cartridge and the automated tape libraries that may
house them.
DFSMStvs: this optional component allows VSAM data sets to be shared
between CICS, batch jobs, and object orientated applications whilst ensuring
the integrity of data.
Data created in this systems are stored in files and this files are stored in a
hierarchical directory format.
File system types supported by the z/OS UNIX:







zFS(zSeries File system): is a set of data that contains the UNIX file
system is a z/OS VSAM data set and because of this it can reside
alongside other z/OS data sets on DASD volume.
HFS(Hierarhichal File System): is the mountable file system phased out
in favor of zFS.
z/OS NFS( z/OS Network file system): allows z/OS to access a remote
UNIX file system using TCP/IP and reference it as if it were part of the
local z/OS directory tree.
TFS(Temporary file system): is temporary, in-memory physical file
system.

Describe security components used to protect data from unauthorized access:

RACF(resource access
control facility) is the primary
component of the IBM Security
Server. Whose role is to provide
appropriate access to the
system’s resources. The RACF
contains “profiles” referenced
whenever there is a request for
a protect ted resource.
SAF(system authorization
facility) is a standalone
product from the z/OS itself
which provides an initial common interface for resource requests.

List the products that can be used to Gain Access to the mainframe:

TSO(Time Sharing
Option): is the initial
access to z/OS
system

The mainframe access is
provided through a 3270
terminal emulator that
connects to the
mainframe through one of
the IBM protocols.
The IBM protocols are
provided by the network
operating system or
through TN3270(an
implementation of Telnet
that use TCP/IP).

From here the user can access
TSO and other z/OS subsystems
such as CICS and IMS regions.
TSO commands are usually
invoked from products such as
ISPF, or within JCL, or from CLISTS
and REXX programs.

ISPF menu option:







View: enables you to view
or browse (no editing) data
stored in partitioned data
sets.
Edit: enables you to
create, display and modify
existing data stored in
partitioned or sequential
data sets.
Utilities: is used for many data set and partitioned data set member purposes
(example: renaming, deleting, allocating, listing).
Command: enables you to enter TSO commands to execute CLIST or REXX
programs.

Another way to access data on the mainframe us using z/OS UNIX shell.
Entering the OMVS command for the
TSO provides access to the z/OS UNIX
shell where shell commands, scripts and
utilities can be run.

job

1. A series of steps, each entailing the execution of a program and possibly the disposition of
data sets.
2. The job control statements define a job.
Job control language
1. The language used to define the operating process of a job. The statements are used to
specify which programs are to run and which data sets they are to use for input and output,
and optionally other parameters to control the way the job is run.
2. (CA) Code used to describe the resources required by a program within an IBM MVS
operating system environment.

JCL (Job Control Language): The language used to define the operating process of a job. The
statements are used to specify which programs are to run and which data sets they are to use
for input and output, and optionally other parameters to control the way the job is run.
DD statement
The job control statement used to associate a data set with a logical file.
JES
Job entry subsystem. The program or task that maintains a spool environment, and through
which programs and operators access that environment.
JES2
One of two job entry subsystems available for MVS systems. Originally based on the Houston
Automatic Spooling Priority system (HASP).
JES2 job log
A listing containing the system log, device and data set allocation details, and (possibly)
resource utilization data for a particular job.
JES3
One of two job entry subsystems available for MVS systems. Originally based on the
Asymmetric Multiprocessing System (ASP).

Commands:
SUBMIT: sends the job to the system for execution
STEPCOP EXEC PGM=”Program Name”: requests a program you name

SYSUT1 DD DSN=PROD.REBMASTER.D2014109, DISP=SHR: is asking to
access an existing data called PROD.REBMASTER.D2014109
SYSUT2 DD DSN=SORTED.REBMASTR.D2014109,
UNIT=SYSDA,SPACE=(TRK,(5,5),RLSE),DISP=(NEW,CATLOG): accesses
existing data called SORTED.REBMASTR.D2014109
SYSIN DD SYSOUT=* : creates some output
How JCL is used to process data

Identify how jobs are submitted to the system and how they are processed by JES

1-The job is submitted to the system manual through job scheduling software or a
starter task.
2-JES2 reads the input data, assigns a job identifier to it and places the job’s JCL
onto the DASD (Direct Access Storage Device: Usually a disk device or a class of disk
devices) dataset called spool.
3-JES2 reads the JCL, analyzes it for any errors, in there are no errors it converts it to
machine language. If JES2 detects any JCL errors, JES2 issues a message and the job
is queued for output processing rather than run.
4-JES2 selects from jobs that are waiting to run and sends them to z/OS for
execution.
5-Any output produced by the job is analyzed and placed in the appropriate queue
by JES2.
6-JES2 selects output for processing (ex. Printing)

7-When the job has completed its process, JES2 frees the spool space assigned to
the job.

Any work performance on the mainframe must be scheduled according to priorities
and the resources available. For z/OS this is automatically performed by the
workload management(WLM).
WLM: manages the processing of workloads in the system according to goals, such
as response time requirements. WLM also manages the use of system resources,
such as processor and storage, to accomplish this goals.

SDSF Panels Functions used by Monitor Batch Job Activity
DA- displays the activity of jobs,
started tasks and TSO users that are
currently running
I- displays jobs, started tasks or TSO
have been submitted for running or
currently executing.
O-displays non-held output produced
jobs, started tasks and TSO users.

users that
are
by

H-displays help output associated
with a job, started task and TSO user.
ST-is a combination of several other SDSF options as it displays jobs, started tasks
and TSO users across a number of different JES queues.
LOG-displays the system log, which contains system console messages and any
operator interactions.

SDSF Display active(DA) panel:

C Pos values indicate the position of the address space and may indicate a job is not
running. Any code beginning with a W indicates that it is on a wait queue. Possible
results are:
IN- Swapped into memory indicating that is currently running
NS- Non-swappable, commonly used for important jobs, for performance reasons
are not allowed to be swapped out of memory
LO- Logical swapped out of memory

If a job hasn’t been submitted or does not appears in the DA panel, access the SDSF
input panel to check if something is delayed its execution. (If you are authorized you
can enter commands on the screen to resolve the reason for the delay)

STATUS field:
HOLD- job on hold
awaiting for manual release
DUP- a job with the
same name is currently
running
Blank- indicates a job
is running unless a resource
constraint is blocking it

If POS has a number
(1,2,3,4...) this indicates the position of the job in the JES2 input queue. The job
highlighted here are waiting for an initiator to become available and the number
indicates the order in which they will be started when it occurs.

This is the SDSF Log option
that enables you to view
the system log in order to

After a job is completed,
SDSF to display the
output produced of the
job (the output of the
job could include system
information relating to the
general running of the job,
program results, reports, or
any data requested by the
various programs that ran).

locate a job.

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