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mvs INTRODUCTION INTRODUCTION EVOLUTION OF IBM MAINFRAME STRUCTURE WHY MAINFRAMES? MAINFRAME OPERATING SYSTEMS LARGE SYSTEMS COMPONENTS CATEGORIES OF PROGRAMMING THE OPERATING SYSTEM Mainframes
•
Oldest form of computer
•
Expensive and powerful
•
Small, Medium, and Large-Program handling
•
Uniprocessor; high-speed storage
•
Can be shared by a wide variety of users
•
System/360, 370, 390 from IBM
EVOLUTION OF IBM MAINFRAME STRUCTURE IBM Mainframe designs have compatible evolution based on System/360,and extended through System/370, System/370-XA, and now System/390. Prior to system/360, which was developed in 1964, there were different families of different systems for scientific computing and commercial data processing
1
mvs
WHY MAINFRAMES? • • • • • • •
Can handle large volumes of data Have high processing power Provide centralized administration and storage Offer superior data management capabilities Can handle different types of workload Have high data bandwidth Monitor data integrity and security
MVS Evolution
• •
1961 OS 360 PCP (Primary Control Program) 1966 OS/MFT (Multiprogramming with a Fixed number of Tasks)
OS/MVT
• • • • • • •
1972 1974 1983 1988 1995 1996 1998
OS/VS1, OS/VS2 R1 (SVS) (SYSTEM/370 OR OS/VS) OS/VS2 R2 (MVS) ((Multiple Virtual Storage) MVS/XA (MVS Extended Architecture) MVS/ESA (MVS Enterprise System Architecture) MVS/ESA 5.2.2 OS/390 1.1 OS/390 2.6
MAINFRAME OPERATING SYSTEMS MVS/XA, MVS/ESA, OS/390
• •
Suitable for production environment Transaction processing
2
mvs • • • • • •
Time sharing Program development Virtual storage concept Multiprogramming, Spooling, time sharing and batch processing Addressing capacity Supports bimodal processing
OS/390 Prior to OS/390, the System/390 world consisted of tons of different products that had to be ordered, installed and maintained separately. The products were updated in different release cycles. OS/390 An Integrated Solution The OS/390 system builds on the strengths of MVS/ESA and provides a complete networkready server environment.
LARGE SYSTEMS COMPONENTS Hardware
• • • • • •
Central Electronic Complex Central processors System controller Central storage Expanded storage Channel subsystem
INPUT/OUTPUT
• •
Control units Devices: DASD, tape, printer
Communication Subsystem
• • • •
Communication controllers Cluster controllers Terminals Multiplxess, modems
SOFTWARE
• • • • • • •
Operating system (like MVS/ESA) System applications Job entry subsystem Communication software Batch applications DB/DC Applications Storage management subsystem
3
mvs CATEGORIES OF PROGRAMMING • •
Batch programming Interactive programming
Batch Programming
• • •
Accepts data for processing in groups called batches and produces o/p grouped into sets. Do not communicate with any user as they execute Once started, supervised by the computer's OS
Interactive programming
• • • •
Designed to communicate with users as they run Issues messages and prompts Allow the end user to communicate new info or change existing info Adapted with CICS
THE OPERATING SYSTEM
Operating System is a maser system program that controls a computer system. When there are a number of jobs to be run in a batch processing, instructions are written to OS among other things,
• • •
Performs system scheduling tasks Handles system interruptions Monitors system status
The Functions of OS are System Management
• • • • •
Starts and shut down the system Manages network interfaces Prioritizes the work in TSO mode Job processing Security management
Resources Management
• • • • • •
Decides which devices to be accessed by the CPU Prioritizes the work for the devices Manages the CPU for the optimum usage Establishes the connectivity. Loads compilers, applications Manages the library routines
Memory management
•
Allocation of memory
4
mvs • • •
De allocation of memory Fragmentation and garbage collection Paging and segmentation.
File Management
• • • • • • • • • •
CREATE DELETE COPY MERGE VIEW ADD EDIT PRINT OPEN CLOSE
System Overview
5
mvs
CONCEPT OF MAINFRAME CPC UNIPROCESSOR MULTIPROCESSING MULTIPROGRAMMING CENTRAL STORAGE VIRTUAL STORAGE PAGING THRESHOLD QUEUES PAGE STEALING PAGE OUT PAGE FAULT PAGE IN SWAPPING SWAP OUT
6
mvs ADDRESS SPACE
CPC The Central Processor Complex (CPC) consists of the central processor and channel subsystems and the storage as the hardware and the system application programs, user programs and other tools as the software. The primary program executing on the system is the Operating System (OS).
UNIPROCESSOR
The CPC processing only one instruction at a time is called uniprocessor system. The OS manages the instructions to be performed and the resources required by the program. Thus having only a single copy of the OS operating system running under single processor is called a uniprocessor. Though it is simple, no backups can be taken in case of system failure.
MULTIPROCESSING
Under one operating system multiple processors can be connected so that simultaneous processes take place, the processors share the central storage and I/O configuration.
7
mvs MULTIPROGRAMMING
With multi programming, multiple programs have to reside in the central storage. When one program is waiting for I/O operation to complete, the system can interrupt that program, store the information about the program so that the next ready to Execute program gets executed. Once the I/O operation is over, the interrupted Program gets executed from the point it got interrupted.
CENTRAL STORAGE
The processor storage where the instruction and data it references must reside, for the instruction to be processed is called the central storage. It is divided in to separate areas called the frames of 4K bytes and each area is identified by a unique address space. Faster access and better performance but the available central storage is very limited.
VIRTUAL STORAGE
8
mvs
Virtual storage is the range of addresses available for the users, where the programs that have capacity, more than the central storage can reside. It is divided in to equal areas of 4K called PAGES. The SVS (Single Virtual Storage) is the first virtual storage that was available to the users. For 24 bit addressing 16 Mega byte addresses is available. The MVS (Multiple Virtual Storage) was introduced, where each user was given a 16 Mega byte address space.
PAGING
9
mvs
At the time of execution the pages from the virtual storage is transferred to the central storage frame and the inactive pages from central storage frame is put back to the Auxiliary storage slot or Expanded storage frame. This process of moving the pages into and out of central storage is called Paging.
THRESHOLD QUEUES
The central storage maintains a queue of frames in order to ensure that a frame is available at the time of allocation. Hence a threshold of frames are reserved for the purpose. When the actually available frames falls below this number, page stealing takes place and when it goes above the threshold the stealing is stopped.
PAGE STEALING It is the process of monitoring the central storage periodically and placing the least recently used page in the available frame queue. The SRM (System Resource Manager) checks the reference bit and maintains a record of how long a page has not been referenced and sets the reference bit to OFF after a certain amount of time. Theses least recently used frames are more prone to be stolen. When a frame with change bit is ON, then it should be saved.
PAGE OUT
10
mvs
The least referenced pages are thus sent to the expanded storage or auxiliary storage in order to maintain the threshold value of available frame queue. This process of transferring the page from the central storage is called the Page Out.
PAGE FAULT When a page is stolen its entry in the page table is marked invalid. A page fault occurs when DAT tries to convert a virtual address to real address to reference the stolen page.
PAGE IN
When a page fault occurs, an available central storage frame is allocated for the requested page and DAT has the capability to bring the page to the central storage from the expanded storage or the auxiliary storage.
SWAPPING
Swapping is the movement of address spaces from and to the central storage depending on the current load on the system.
11
mvs SWAP OUT
Swap out is the movement of the address space from the central storage to the expanded storage or auxiliary storage. If a user is waiting for input or output for a long duration then the SRM (System Resource Manager) takes out the address space from central storage frame.
ADDRESS SPACE
• • • • • • •
A 2-gigabyte range of virtual address is called an address space. An address space is provides the capability for a program to address up to 2 GB of virtual storage. An address space represents a user in the system. Frames of central storage will be occupied by pages from many different address spaces. The address space provides the addressing structure that will be used by programs mapped into that address space. The address space addresses are virtual addresses. As the program executes, the virtual addresses will be converted to real addresses. The system area called the common area maps the executable MVS code and the control blocks and work areas needed by all address spaces in the system. The common area is mapped around the 16 MB line. MYPROG will be mapped into an address space and will probably use only a small part of the 2-gigabyte addressing range. My address space has addressability to MVS system functions, such as the nucleus and the link pack areas that are mapped in the common area of every address space.
12
•
Oldest form of computer
•
Expensive and powerful
•
Small, Medium, and Large-Program handling
•
Uniprocessor; high-speed storage
•
Can be shared by a wide variety of users
•
System/360, 370, 390 from IBM
EVOLUTION OF IBM MAINFRAME STRUCTURE IBM Mainframe designs have compatible evolution based on System/360,and extended through System/370, System/370-XA, and now System/390. Prior to system/360, which was developed in 1964, there were different families of different systems for scientific computing and commercial data processing
1
mvs
WHY MAINFRAMES? • • • • • • •
Can handle large volumes of data Have high processing power Provide centralized administration and storage Offer superior data management capabilities Can handle different types of workload Have high data bandwidth Monitor data integrity and security
MVS Evolution
• •
1961 OS 360 PCP (Primary Control Program) 1966 OS/MFT (Multiprogramming with a Fixed number of Tasks)
OS/MVT
• • • • • • •
1972 1974 1983 1988 1995 1996 1998
OS/VS1, OS/VS2 R1 (SVS) (SYSTEM/370 OR OS/VS) OS/VS2 R2 (MVS) ((Multiple Virtual Storage) MVS/XA (MVS Extended Architecture) MVS/ESA (MVS Enterprise System Architecture) MVS/ESA 5.2.2 OS/390 1.1 OS/390 2.6
MAINFRAME OPERATING SYSTEMS MVS/XA, MVS/ESA, OS/390
• •
Suitable for production environment Transaction processing
2
mvs • • • • • •
Time sharing Program development Virtual storage concept Multiprogramming, Spooling, time sharing and batch processing Addressing capacity Supports bimodal processing
OS/390 Prior to OS/390, the System/390 world consisted of tons of different products that had to be ordered, installed and maintained separately. The products were updated in different release cycles. OS/390 An Integrated Solution The OS/390 system builds on the strengths of MVS/ESA and provides a complete networkready server environment.
LARGE SYSTEMS COMPONENTS Hardware
• • • • • •
Central Electronic Complex Central processors System controller Central storage Expanded storage Channel subsystem
INPUT/OUTPUT
• •
Control units Devices: DASD, tape, printer
Communication Subsystem
• • • •
Communication controllers Cluster controllers Terminals Multiplxess, modems
SOFTWARE
• • • • • • •
Operating system (like MVS/ESA) System applications Job entry subsystem Communication software Batch applications DB/DC Applications Storage management subsystem
3
mvs CATEGORIES OF PROGRAMMING • •
Batch programming Interactive programming
Batch Programming
• • •
Accepts data for processing in groups called batches and produces o/p grouped into sets. Do not communicate with any user as they execute Once started, supervised by the computer's OS
Interactive programming
• • • •
Designed to communicate with users as they run Issues messages and prompts Allow the end user to communicate new info or change existing info Adapted with CICS
THE OPERATING SYSTEM
Operating System is a maser system program that controls a computer system. When there are a number of jobs to be run in a batch processing, instructions are written to OS among other things,
• • •
Performs system scheduling tasks Handles system interruptions Monitors system status
The Functions of OS are System Management
• • • • •
Starts and shut down the system Manages network interfaces Prioritizes the work in TSO mode Job processing Security management
Resources Management
• • • • • •
Decides which devices to be accessed by the CPU Prioritizes the work for the devices Manages the CPU for the optimum usage Establishes the connectivity. Loads compilers, applications Manages the library routines
Memory management
•
Allocation of memory
4
mvs • • •
De allocation of memory Fragmentation and garbage collection Paging and segmentation.
File Management
• • • • • • • • • •
CREATE DELETE COPY MERGE VIEW ADD EDIT PRINT OPEN CLOSE
System Overview
5
mvs
CONCEPT OF MAINFRAME CPC UNIPROCESSOR MULTIPROCESSING MULTIPROGRAMMING CENTRAL STORAGE VIRTUAL STORAGE PAGING THRESHOLD QUEUES PAGE STEALING PAGE OUT PAGE FAULT PAGE IN SWAPPING SWAP OUT
6
mvs ADDRESS SPACE
CPC The Central Processor Complex (CPC) consists of the central processor and channel subsystems and the storage as the hardware and the system application programs, user programs and other tools as the software. The primary program executing on the system is the Operating System (OS).
UNIPROCESSOR
The CPC processing only one instruction at a time is called uniprocessor system. The OS manages the instructions to be performed and the resources required by the program. Thus having only a single copy of the OS operating system running under single processor is called a uniprocessor. Though it is simple, no backups can be taken in case of system failure.
MULTIPROCESSING
Under one operating system multiple processors can be connected so that simultaneous processes take place, the processors share the central storage and I/O configuration.
7
mvs MULTIPROGRAMMING
With multi programming, multiple programs have to reside in the central storage. When one program is waiting for I/O operation to complete, the system can interrupt that program, store the information about the program so that the next ready to Execute program gets executed. Once the I/O operation is over, the interrupted Program gets executed from the point it got interrupted.
CENTRAL STORAGE
The processor storage where the instruction and data it references must reside, for the instruction to be processed is called the central storage. It is divided in to separate areas called the frames of 4K bytes and each area is identified by a unique address space. Faster access and better performance but the available central storage is very limited.
VIRTUAL STORAGE
8
mvs
Virtual storage is the range of addresses available for the users, where the programs that have capacity, more than the central storage can reside. It is divided in to equal areas of 4K called PAGES. The SVS (Single Virtual Storage) is the first virtual storage that was available to the users. For 24 bit addressing 16 Mega byte addresses is available. The MVS (Multiple Virtual Storage) was introduced, where each user was given a 16 Mega byte address space.
PAGING
9
mvs
At the time of execution the pages from the virtual storage is transferred to the central storage frame and the inactive pages from central storage frame is put back to the Auxiliary storage slot or Expanded storage frame. This process of moving the pages into and out of central storage is called Paging.
THRESHOLD QUEUES
The central storage maintains a queue of frames in order to ensure that a frame is available at the time of allocation. Hence a threshold of frames are reserved for the purpose. When the actually available frames falls below this number, page stealing takes place and when it goes above the threshold the stealing is stopped.
PAGE STEALING It is the process of monitoring the central storage periodically and placing the least recently used page in the available frame queue. The SRM (System Resource Manager) checks the reference bit and maintains a record of how long a page has not been referenced and sets the reference bit to OFF after a certain amount of time. Theses least recently used frames are more prone to be stolen. When a frame with change bit is ON, then it should be saved.
PAGE OUT
10
mvs
The least referenced pages are thus sent to the expanded storage or auxiliary storage in order to maintain the threshold value of available frame queue. This process of transferring the page from the central storage is called the Page Out.
PAGE FAULT When a page is stolen its entry in the page table is marked invalid. A page fault occurs when DAT tries to convert a virtual address to real address to reference the stolen page.
PAGE IN
When a page fault occurs, an available central storage frame is allocated for the requested page and DAT has the capability to bring the page to the central storage from the expanded storage or the auxiliary storage.
SWAPPING
Swapping is the movement of address spaces from and to the central storage depending on the current load on the system.
11
mvs SWAP OUT
Swap out is the movement of the address space from the central storage to the expanded storage or auxiliary storage. If a user is waiting for input or output for a long duration then the SRM (System Resource Manager) takes out the address space from central storage frame.
ADDRESS SPACE
• • • • • • •
A 2-gigabyte range of virtual address is called an address space. An address space is provides the capability for a program to address up to 2 GB of virtual storage. An address space represents a user in the system. Frames of central storage will be occupied by pages from many different address spaces. The address space provides the addressing structure that will be used by programs mapped into that address space. The address space addresses are virtual addresses. As the program executes, the virtual addresses will be converted to real addresses. The system area called the common area maps the executable MVS code and the control blocks and work areas needed by all address spaces in the system. The common area is mapped around the 16 MB line. MYPROG will be mapped into an address space and will probably use only a small part of the 2-gigabyte addressing range. My address space has addressability to MVS system functions, such as the nucleus and the link pack areas that are mapped in the common area of every address space.
12
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