IBM latest mainframe:
- Other Names:
- –“Big Iron”
- –“Enterprise Server”
- –“Main Server” or just “Server”
- –IBM System Z
- “Z” stands for Zero Down Time
- IBM latest mainframe:
- IBM® z13
Types of businesses using mainframes
- Health care
- Public utilities
- and a multitude of other public and private enterprises
- the mainframe computer continues to form the foundation of modern business
- 1950’s: Mainframe development started
- First Generation- IBM 705 followed by IBM 1401
- 1960’s: S/360 style
- Third generation mainframe
- Commercial or Scientific
- 1970’s: S/370 style
- Next Generation
- 1980’s–4341, 4381, 3033 etc
- 1990’s–S/390 style
- 2000’s–z/9 z/10 z/13 series
The term mainframe in this text means computers that can:
- Supports thousands of applications
- Host many users
- Input/output devices to simultaneously serve thousands of users
- Central data repository
- Primary hub
- Found in a corporation's data processing center
- Houses commercial databases, transaction server, and applications
- Linked to users through less powerful devices such as workstations or terminals
Implies a centralized form of
- Computing (supports Cloud computing)
- Saves customers from having to manage updates to more than one copy of their business data
- Increases the likelihood that the data is current
Two categories of workload:
- Batch processing
- Online Transaction processing
- MTBF 99.999% (Mean Time Between Failure)
- Reduces SPOF (Single Point of Failure)
- Provides for CoD (Capacity on Demand)
- Reduces TCO (Total Cost of Ownership)
- 1960s, the course of computing history changed dramatically
- mainframe manufacturers began to standardize the hardware and software they offered to customers.
- The introduction of the IBM System/360™ (or S/360™) in 1964 –Signaled the start of the third generation
- –The first general purpose computers
- Could perform both types of computing
- –Use microcode (firmware) for machine instructions
- Older mainframes required:
- Large amounts of space
- High power consumption
- High air-conditioning requirements
- Occupied 2,000 to 10,000 square feet of space
Mainframes and first programming languages
Support for other languages
- Mainframes and first programming languages:
- Support for other languages:
- CICS (Customer Information Control System)
- Transaction Processing System (C.I.C.S.)
Problems with older O/S
- Jobs had to wait for information to be
- read in from,
- or written out to, a device such as a tape drive or printer.
- Input and output (I/O) take a long time compared to the electronic speed of the processor.
- jobs waited for I/O, the processor was idle (wasted time)
- No multiprocessor or multitasking
- The operating system
- processed each request or job as a unit
- did not start the next job until the one being processed had completed.
- This arrangement worked well when a job could execute continuously from start to completion
z/OS Multiprocessing / Multitasking
- Controlled by O/S:
- Support for up to 64 engines in a single logical partition
- Up to 1.0 terabyte (TB) of real memory per logical partition
- Software designed to relieve requirements of O/S:
- JES2(3) Job Entry Subsystem
- RACF Resource Access Control Facility (Security)
–Spooling Queues for input and output jobs
PF key assignments: Function Key
- Enter Ctrl (right side)
- Exit, end, or return PF3
- Help PF1
- PA1 or Attention Alt-Ins or Esc
- PA2 Alt-Home Cursor movement Tab or Enter
- Clear Pause
- Page up PF7
- Page down PF8
- Scroll left PF10
- Scroll right PF11
- Reset locked keyboard Ctrl (left side)
- TSO: Time Sharing Option
- TSO divides available CPU time and allocates the slices to users.
- time slices are very short
- The system cycles through the requesting users very quick
- It appears as if they have simultaneous access
- An on-line terminal-oriented system
- –Gives access to IBM Mainframe MVS, OS/390, ZOS files and programs, job submission and the print spool
- –Generally used for creating and editing files and programs and for testing
- A multi-user environment
- –for the IBM MVS mainframe operating system.
- –New name z/OS Operating System
- Interactive System Productivity Facility
- a menu driven full screen interface
- interfaces to the most commonly accessed TSO features.
- includes facilities to:
- –Create / edit source code for programming
- –Create and Edit data files
- –Browse member, browse files
- –Manage data and programs
- Submit jobs for processing (COBOL Compiles)
- Retrieve the results
- Delete unwanted results
- Has a editor
- The ISPF editor facility allows you to edit
- –source code, JCL, and Data
- Editing functions
- –Insert lines
- –Repeat lines
- –Copying lines
- –Moving lines
- –and deleting lines
- You may customize the environment through edit modes and the creation of edit profiles.
- Advanced techniques like
- –finding and changing text
- –excluding and redisplaying lines
- -as well as shifting text will be covered
ISPF utilities include
- –library utilities,
- –data set utilities,
- –move/copy utility,
- –data set list utility,
- –and compare/search utilities.
- –submit a job for background processing,
- –monitor the status of a job while it is waiting, executing, or waiting for its output to print,
- –and how to retrieve the output for a job that is completed
- System Display and Search Facility)
- –monitor, manage, and control your z/OS MVS/JES2 system JES
- –Job Entry Subsystem
- SDSF panels provide current information about
- –Jobs and output
- –devices (including printers, punches, initiators, lines, spool offloaders and spool volumes)
- –and system resources
- With SDSF panels, there is no need to learn or remember complex command syntax.
- –action characters
- –overtypeable fields
- –action bar, pull-downsand pop-up windows allow you to select available functions
- Job Entry Subsystem
- JES is a systems management tool
- provides you with information to monitor, manage, and control your z/OS
- you can:
- –Control job processing (hold, release, cancel, and purge jobs).
- –Monitor jobs while they are running.
- –Browse jobs without printing.
- JES-managed initiators (JES2), job classes, and job class groups (JES3).
- Control printers, punches, functional subsystems (JES3), and NJE resources.
- Control your JES spool configuration
- consists of panels that provide immediate and current information about
- –jobs, –printers, –queues, –and resources in z/OS
- You use series of panels
- –you can enter (E)JES commands to control the processing of jobs and the operation of system resources
- You can also issue system commands from the (E)JES panels.
- With (E)JES you can easily access and modify
- –all attributes for jobs,
- –started tasks,
- –TSO users,
- –APPC/MVS transaction jobs,
- –or processes running under Unix System Services residing anywhere
- Job Control Language
- The language used by the z/OS, MVS mainframe
- –Used to compile your source code
- –Used to execute (run) jobs to
- –Not user friendly
- Used to execute the various jobs required by the user
- Program Development Facility
- provides the application developer with services necessary to create and test applications
- Different activities for the user include:
- generate tables
- manage data sets
- create test messages
- trace and debug applications
- The center of the PDF is the ISPF Primary Option Menu
- The menu contains a list of options which may be customized
- The main menu on one z/OS system might not match the one on another system.
Standard options for the PDF Main Menu are
- Dialog Test
- IBM Products
Note: These options may vary between systems
- Settings: Used to display and change ISPF parameters
- You can change key definitions and display styles
- View: Allows you to view data sets
- Edit: Allows you to create or update data sets
- Utilities: Utility system and data set management functions, such as printing, renaming, or deleting data sets
- Foreground: Used to interactively run language processing programs such as COBOL.
- Batch: Generates and submits batch jobs through job control statements
- Command: Enter TSO commands while ISPF remains active
You can navigate through ISPF in four different methods.
- Action Bars
- Selection by Option Code
- Function Keys
Option vs Command:
- The command area for menu screens is identified by:
- Option ===>
- For other screens, ISPF identifies the command area by:
- Command ===>
- You can get to the command area quickly by pressing the Home key
- No matter where the cursor may be, the home key will immediately place the cursor in the command area
Modal pop-up windows:
Modeless pop-up windows:
- Modal pop-up windows:
- require user interaction or some kind of reply before the underlying dialog continues.
- Modeless pop-up windows:
- allow you to continue to interact with the underlying dialog before you choose to interact with the pop-up
- PA1 Attention: Interrupt the current position.
- PA2 Reshow: Redisplay the current screen.
- PF1/13 Help: Enter the tutorial, or view help.
- PF2/14 Split: Enter split screen mode.
- PF3/15 End: Terminate the current operation.
- PA4/16 Return: Return to the primary option menu.
- PA7/19 Up: Move the screen window up.
- PF8/20 Down: Move the screen window down.
- PF9/21 Swap: Activate the other logical screen in split screen mode.
- PF10/22 Left: Move the screen window left.
- PF11/23 Right: Move the screen window right.
- PF12/24 Retrieve: Redisplay the last issued ISPF command.
- To enter split-screen mode
- You place the cursor on the line where you want the split to occur
- Then press PF2
- Immediately the screen splits into two logical screens, and each logical screen is an independent session
- To switch between screens press PF9.
- To end split screen mode
- Simply end one of the sessions by typing ‘exit’ on the command line
- Or pressing F3 from the Primary Options Menu.
Data Sets in z/OS
- In the z/OS environment, files are known as data sets
- z/OS lets you maintain two types of data sets under TSO:
- Punched Cards
- 80 columns in size
- Used in an MVS system in the 1960s existed as 80-column punched cards
- Today's JCL and program source code on a modern z/OS system is maintained as a file of 80-byte records.
- Every statement is a full 80 bytes long even if it is completely blank.
- Records of a file can be retrieved only in the same order they were written
- To process a record somewhere within the file, you have to read all of the preceding records
- A partitioned data set (PDS) consists of
- A directory and
- One or more members
- A PDS is also called a library
- There are no subdirectories
- file naming and the use of partitioned data sets support all the processing that occurs on a mainframe under z/OS
- Each member is functionally the same as a sequential data set:
- you can process an individual member of a partitioned data set as if it were a sequential data set
- you can process the entire library, the entire PDS, as a single file
Data Sets General Information:
- The minimum allocation for a data set is one track of disk space
- For a small file that contains only a small amount of information, much space can be wasted if it is stored in a data set all by itself.
- Instead it can be stored as one of many members in a partitioned data set
- Each partitioned data set contains a directory and data area.
- The directory maintains housekeeping information about the members stored in the data area.
- It stores an index of member names and their locations.
Partitioned Dataset naming convention:
- Standard TSO data set naming calls for three qualifiers within the name of the data set
- Qualifiers can be up to eight characters long and when you specify a data set name, you separate the qualifiers by periods.
- The data set name consists of three qualifiers listed below.
- High-level Qualifier
- User Determined Qualifier
- Type of Data
- Example: COMP1081.FALL2013.DATA
Partitioned data sets and members:
- Appear to the z/OS operating system to be no different than any other type of data set
- By seeing the name it is not possible to tell absolutely if the data set is partitioned or not
- The operating system has the information internally about its organization, but this is not necessarily reflected in the name
- In order to deal with a specific member of a partitioned data set, the member name is placed at the end of the data set name inside parentheses
- The member name, which is the name in parentheses, can be up to eight characters long, and must start with a letter
The management of the PDS:
- Its creation and internal organization, is handled by the z/OS operating system
- When a member of a PDS is retrieved or browsed, only the name is required
- The z/OS operating system handles its extraction from the data set structure
- Many times programmers maintain two PDSs for a project
- One is for source code, and it will carry a name as the third qualifier like COBOL, FORT, PLI, or ASM
- Additionally, there will be a PDS for JCL statements. These carry a name of "CNTL" as the third qualifier
- The standard names cause ISPF to default to convenient screen presentation formats for each language
ISPF and Datasets: View Entry Panel
- The View Entry Panel appears when you select View (option 1) from the ISPF Primary Option Menu.
- This option facilitates viewing and browsing of a data set, but does not provide the ability to edit or change data
- Two areas of particular interest here are the fields in the panel and the action bar at the top of the panel.
ISPF Library section
- Permits you to enter a data set name
- The project ID identifies the project associated with the data set.
- It usually defaults to the user ID from your LOGON command
- The three components of the data set name
- and Type, are strung together to form the z/OS data set name.
- Another example:
Specify a Member Name
- If the data set is partitioned, you can specify the name of the member in the Member field
- You may also enter a pattern for the member name
- A pattern consists of a partial member name plus the symbols * or % or both (wildcards)
- For example:
- the member name PAY* will select all members that begin with the three letters P-A-Y
- If the data set you specify is partitioned, and you specify a pattern of the member name, or if you do not specify a member name at all, you will receive a member list
- After you have selected the member you want to display, the browse panel displays the first 22 lines of the data
- F8 moves forward through the file
- F7 moves you backup (upwards) through the file
- The heading line displays the data set name, current line position, and current columns displayed
- In the following screen, only browsing is allowed
- You are not permitted to edit the member
View member data:
- Scrolling functions let you specify both the direction and amount you move as you peruse the data
- PF7 and PF8 move the window up and down respectively
- PF10 and PF11 move it left and right
- You may specify the amount of the scroll by entering a value in the SCROLL field at the lower right hand side
- The default value is HALF
- This means that when you press any of the function keys mentioned above, the window moves a half page in the direction desired
You can use the FIND command to:
- Search a member for a specific string of characters
- You type FIND at the command line followed by the string
- If the search string contains blanks or characters, enclose it in either single or double quotes.
- An example is:
- FIND "PROCEDURE DIVISION"
- Use “ “ to include spaces
- This command will find the next line that contains the target string
- You can also add one of the following qualifiers after the search string
- NEXT, PREV, FIRST, LAST, ALL