Information Systems

Z/Os architecture includes all of ESA/390 and the following extensions
• IBM’s high-end server OS
• Robust IBM e-server Z series mainframe OS for e-business
• Highly secure scalable high performance base to deploy internet + java technology-enabled applications
• Z/OS takes advantage of latest open s/w technologies like EJB/XML/HTML/UNICODE/IP network etc.
• Cryptographic services and distributed print services, storage management, and parallel sysplex availability
• 64 bit general registers and control registers
• 64 bit addressing mode in addition to 24 bit and 31 bit addressing modes of ESA/390 which are carried forward to Z/OS architecture
• The program status word (PSW) is expanded to 16 bytes to contain larger instruction address
• Upto three levels of DAT tables called Region Tables for translating 64 bit virtual address
• Trimodal addressing as against bimodal addressing
• Ability to switch between 24, 31, and 31 bit addressing
Logically a system consists of the main storage, one or more CPUs and channel subsystems.
Addressing: Absolute, real and virtual
Address translation converts virtual addressing to real addressing and prefixes converts real addressing to absolute addressing
A 24 bit or 31 bit virtual address is expanded to 64 bits by appending 40 or 33 zeroes on the left before it is translated by means of DAT process and 24 and 31 bit absolute address is expanded to 64 bits before its is transformed by prefixing. A 24 or 31 bit absolute address is expanded to 64 bits before main storage is accessed

Disk operating systems/360
• Single task (only one program at a time)
• Simple OS, with minimum storage and CPU requirements
OS/360 for system/360
• PCP (Primary control program) ran only one task at a time
• Multiple fixed tasks – up to 15 tasks, with fixed time-slices for each task
• Partitions have to be configured before start-up
MVS (Multiple virtual storage) for system/370 (originally OS/VS2)
• Multiple variable tasks – number of tasks, and their time-slices can change dynamically
• Each user/task can have virtually al the memory of 16MB
• This concept of multiple users/tasks using the virtual memory is called MVS
• This brought in the concept of address space – area where the program runs
MVS/XA (extended architecture) for system 370/XA
• Each user/task can have virtually all the memory of 2GB
• Concept of data spaces – areas for storing huge files in memory
MVS/ESA (Enterprise system architecture) for system 370/ESA and system 390/ESA
• Uses hyperspace – data buffering to avoid file I/O
• Huge files are stored in memory, and written to disk only when not needed
Z/OS architecture is an evolutionary upgrade of 390/ESA architecture
• It is IBM’s high end server OS
• Robust IBM e-server Z-series mainframe OS for e-business
• Highly secure, scalable, high performance base to deploy
• Internet + Java technology-enabled applications

Virtual storage
• It is a technique that lets a processor simulate a large amount of main storage from a smaller installed main storage.
• Implementation: Uses disk storage as an extension of main storage
• At any point in time, only one program and its data is required in the main storage

Multiprogramming
• It is a technique that lets more than one program run at the same time
• I/O devices are much slower than processor

Spooling
• It is a facility provided to make efficient use of the output devices.
• Technique that intercepts the printer output and re-directs to a disk file
• Each program’s output is stored separately
• Facilities effective sharing of output devices and provides better system throughput

Batch processing
• The necessary information for batch processing is provided through JCL
• Is managed by the system’s job scheduler which makes decision about the order in which the job should be executed based on the job priority and class
• Is a non-interactive and offline mode of data processing

Time sharing
• Each user accessing the system through a terminal device gets a time slice repeatedly
• At the background the processing is still done in the batch mode

It’s still a wonder that how a machine can handle millions and millions of instructions per second. But they made it by inventing Mainframe computers. These are large room size computers which can handle large volumes of data. It has more access to storage space and Input-Output devices. Mainframes are mainly used in insurance companies, banks, airline and railway reservation systems, etc.
Eg., These are largely used in banks. A bank can have millions of customers. Customer details such as bank balance, withdrawals, and account information were stored earlier in account books. But now a day, these are stored in mainframe computers which has large number of storage capacity. Accessing it is also as simple as that and much faster than other systems. By this, a customer of an International bank who has an account in Los Angles can make a trip to India and withdraw/deposit money in its branch located in Chennai or any other part of the world. Online transactions are also made easy by handling millions and millions of instructions per second. Hence large organizations rely on this room size computers.

ADO.NET is data access technology it is evolution from DAO to RDO to ADO

DAO- Data Access Objects
RDO-Remote Data Object
ADO-ActiveX Data Objects
ADO.NET-Not an acronym
ADO.NET Features
•ADO.NET supports both connected and disconnected solution
•It has tight integration with XML and .Net Framework
•HTTP is used to transport XML between layers
•ADO.NET is managed library of code and has same rules as managed library Connected Layer
•In this our base code will explicitly connected with a data base, the connection is explicitly opened and closed
•It is achieved using Data Reader objects to get records from data store using forward-only, read-only approach

Disconnected Layer
•The disconnected layer is achieved using Dataset. Dataset is local copy of any number of related data tables
•Once the user gets Dataset object it is completely disconnected from the DBMS
•the connection is opened and closed automatically on our behalf
•Data adapter objects are used to fill a Data set with Data Table
•Using Dataset the client tier is able to update and modify its contents of data source while it is disconnected, and it can submit the modified data back using related data adapter
•The main advantage of this layer is data is manipulated without incurring the network traffic

The control concept of control systems also applies to Thermal power.  In that way, there are certain ways in which the thermal power plant is to be controlled

1. Controlling the power generated

First, the power generated needs to be controlled in MW (megawatt). It is not possible to store power. Therefore, the power depends on load on the grid. The load/generation decides the frequency of the grid which is actually controlled by the turbine. The voltage is controlled by the generator and the frequency is controlled by the grid

2. Controlling the steam flow

The power generated directly depends on the steam flow. Turbine valves are throttled (mechanism which restricts the speed or the power of engines) to control the steam flow

3. Controlling steam pressure

Controlling steam pressure depends on the steam flow. The amount of the steam flow decides its pressure. More flow increases the pressure and less flow decreases

4. Need to control the fuel/Air inputs to the boiler

There is a necessity to control the fuel or the air inputs to the boiler (a device that generates steam)

5. Need to control feed water flow to boiler

With “Supervisory Control” primary loop control is returned to analog controllers, while computer monitors the process & adjusts the set points. Computer is relieved from computational tasks & can be utilized for process optimization & plant management

In a Supervisory Control System, Analog control subsystem& panel instrumentation is used for controlling but it is interfaced to a Supervisory Control Computer through interfacing hardware. This Supervisory Control computer provides the facility for monitoring process (which provides the process mimics on the video display units for operators with features like Alarm Handling, Data Storage)

Drawbacks

• Extensive wiring between analog controllers & other instrumentation to the computer system
• Interfacing Multiple Vendor sub-system-Interfacing one vendors computer system to another vendors analog instrumentation
• Costly than DDC

Hierarchical Computer control System

• A hierarchical system is network of process and/or information management computer systems integrated to serve a common functions like management and control of large refineries, pipeline network, energy production facilities for whole country
• Information passed from primary level of process monitoring & control, up through supervisory levels, to decision making/top management level & vice versa
• With hierarchical systems, primary computers provide direct control of process & can be DDC, supervisory or microprocessor base

Drawbacks

• De-centralized control But not centralized & de-centralized control
• Impractical redundancy

To provide a safe shutdown of the system or tripping of equipment, when the operating constraints are violated. The requirements are availability and integrity. Dual redundant, triple redundant or quadruple redundant systems are available. Features like memory test, self test, functionality test are done routinely to test the integrity of the system

Protection in power plant – overview

• Plant Level
• Subsystem Level

1. Boiler Safety
2. BMS – Burner Management System – Guided by NFPA guidelines
3. Interlocks and Protection for Mills
4. EMS – Electromagnetic Safety Valves

• Turbine and Generator Protection

1. Over-Speed
2. Low Vacuum
3. Low LO pressure
4. Steam temp. Trips
5. Seal oil/H2 Diff Pressure
6. Electrical Trips of Generator

• Shutdown Sequences
• Individual Equipment Level

1. ID Fans
2. FD Fans
3. PA Fans
4. Mills
5. BFP
6. CEP etc.,

Alarm systems

• Alarm System – alerts the operator about a trend towards a operating constraint.
• Alarm Management – Very important – provide Alarm priority, Grouping and action plan for each alarm.
• Types

Standalone

• Hardware based
• Software base

Integrated

Alarm Sequences & Standards

• Normal Sequence
• Ring-Back Sequence
• First- Up Sequence

Power plants are controlled by control systems which provide a manual and automatic control of plant

• Maintain an adequate margin from safety and operational constraints – Control System
• Monitor these margins and plant conditions and provide immediate indications and records – Indications, Recording and historization
• Draw the attention of the operator by an Alarm System to any unacceptable reduction in the margins – Alarming
• Shutdown the plant, if Operating Constraint is violated – Safety and Shutdown system

Types of controls

• Analog Control –  Controls a particular parameter as per Set point

• Binary Control

1. Sequence Control – For Startup and Shutdown
2. Motor Control – For Motor Operated Devices

• Permissive
• Interlocks
• Protection

• Protection System – Trips the system

Control Islands in Conventional TPP

• Boiler
• Steam Turbine
• Balance of plant

1. Regenerative system
2. Cooling System
3. Various Auxiliaries

• Misc. Systems

1. Fuel Handling System
2. Ash Handling System
3. Nox Reduction System

Integration of Power Plant Controls

• Co-ordinated Control Mode

1. Integrates Boiler and Turbine Operations
2. Set point received from Unit Load Dispatch Center

• Sliding Pressure Operation for Power Plant

1. Complete control operation by Boiler itself
2. Turbine valves are fully open except for the Pressure Protection

• Integration with Enterprise Level Control – Private Power Bidding

• Integration with Grid level Control

What is DCS ?

Functionally and physically separate automatic process controllers, process monitoring and data logging equipment connected with each other to share relevant information for optimum plant control is called distribution control system

How is DCS ?

• Microprocessor based DCS Systems are a form of DDC that divide data acquisition & control functions among a number of independently operating microprocessor controllers. The controllers are linked together with a data highway that is routed through the plant & connected to the operators console in the control building
• Basically DCS is task partitioning, the breaking up of duties of mainframe computer into many smaller tasks distributed throughout the system
• DCS can be called a computer, but it is no longer a single mainframe.  Instead, many small computers are distributed throughout the remote area installations, sharing the work that the mainframe had to do alone. In fact, even if central station facilities breakdown, remote control operation will continue without interruption

Why DCS ?

• Dominates drawbacks of DDC, Supervisory & Computer control system
• Cost: costless as compared to features they provide
• Versatility: Process plant control, Start-Up, Shutdown & Multifunction capability (Logic, sequence, loop controller, data logger etc.).Used for advanced control, optimization, management level
• Expandability: Handles hundreds of IOs & Used in number of industrial process control application
• Flexibility : Supports new technologies

Nowadays DCS is nothing but Distributed computer control System