Transaction Processing System



Transaction Processing SystemMIS Term PaperShaheed Sukhdev College of Business StudiesSubmitted to: Ms. Neha Submitted by: Aaina Aggarwal (4939) Pratiksha Sharma (4940) BBS 3FB 2011AcknowledgementFirstly, my deepest gratitude to my project mentors; Ms. Neha, for her invaluable help, guidance and support. Without her constant this project would never have come to fruition.I would also thank my college “Shaheed Sukhdev College of Business Studies” for giving me an opportunity to have an enriching experience in terms of this project.Last but not the least, thank you Mummy and Papa and all my family members and friends for always being there for me. It is because of each one of you that this project was made possible.Thank you!! Table of Contents TOC \h \z \t "Title,1" Acknowledgement PAGEREF _Toc290791120 \h 2Table of Contents PAGEREF _Toc290791121 \h 3Introduction PAGEREF _Toc290791122 \h 4Characteristics & Acid Test PAGEREF _Toc290791123 \h 5Process of TPS PAGEREF _Toc290791124 \h 6Types of Processing PAGEREF _Toc290791125 \h 9Storage & Retrieval of Data PAGEREF _Toc290791126 \h 11Back up & Recovery PAGEREF _Toc290791127 \h 12TPS V/s DSS PAGEREF _Toc290791128 \h 14References PAGEREF _Toc290791129 \h 16APPENDIX PAGEREF _Toc290791130 \h 17Introduction Whenever two people make an exchange, it is called a transaction. Transactions are important events for a company, and collecting data about them is called transaction processing. Examples of transactions include making a purchase at a store, withdrawing money from a checking account, making a payment to creditor, or paying an employee. Because transactions generally involve an exchange of money, it is critical that the data be protected during transmission and stored carefully so that it cannot be altered. It is also critical that the data be saved so that managers can verify the data if any conflicts arise. Also, the sales and purchase data from the foundation of the accounting and financial systems of every company, so the system must be able to produce the standard reports. Company, is an advanced system that records and processes insurance-related transactions. Filing and processing insurance claims is a highly information-intensive process in which every step generates new data or modifies existing data. CareNet allows the company to accurately capture this data and disseminate it at the right time to its 7 million clients. The information generated by CareNet is useful both to employees of Travelers Insurance and to its clients. A Travelers employee can access the system and look at the latest transaction; an authorized client can also access CareNet to study the status of his or her insurance claim. This system, therefore, spans organizational boundaries and provides information to both internal external entities. So when we are talking about the transactions of an organization in computerized manner, we talk about Transaction Processing System, popularly known as TPS. A transaction processing system is a type of information system. TPSs collect, store, modify, and retrieve the transactions of an organization. A transaction is an event that generates or modifies data that is eventually stored in an information system. To be considered a transaction processing system the computer must pass the ACID test. The essence of a transaction program is that it manages data that must be left in a consistent state. E.g. if an electronic payment is made, the amount must be both withdrawn from one account and added to the other; it cannot complete only one of those steps. Either both must occur, or neither. In case of a failure preventing transaction completion, the partially executed transaction must be 'rolled back' by the TPS. While this type of integrity must be provided also for batch transaction processing, it is particularly important for online processing: if e.g. an airline seat reservation system is accessed by multiple operators, after an empty seat inquiry, the seat reservation data must be locked until the reservation is made, otherwise another user may get the impression a seat is still free while it is actually being booked at the time. Without proper transaction monitoring, double bookings may occur. Other transaction monitor functions include deadlock detection and resolution (deadlocks may be inevitable in certain cases of cross-dependence on data), and transaction logging (in 'journals') for 'forward recovery' in case of massive failures. Transaction Processing is not limited to application programs. The 'journaled file system' provided with IBMs AIX Unix operating system employs similar techniques to maintain file system integrity, including a journal.Characteristics & Acid TestTransaction processing systems offer enterprises the means to rapidly process transactions to ensure the smooth flow of data and the progression of processes throughout the enterprise. Typically, a TPS will exhibit the following characteristics:Rapid Processing- The rapid processing of transactions is vital to the success of any enterprise – now more than ever, in the face of advancing technology and customer demand for immediate action. TPS systems are designed to process transactions virtually instantly to ensure that customer data is available to the processes that require it.Reliability- Similarly, customers will not tolerate mistakes. TPS systems must be designed to ensure that not only do transactions never slip past the net, but that the systems themselves remain operational permanently. TPS systems are therefore designed to incorporate comprehensive safeguards and disaster recovery systems. These measures keep the failure rate well within tolerance levels.Standardisation- Transactions must be processed in the same way each time to maximise efficiency. To ensure this, TPS interfaces are designed to acquire identical data for each transaction, regardless of the customer.Controlled Access- Since TPS systems can be such a powerful business tool, access must be restricted to only those employees who require their use. Restricted access to the system ensures that employees who lack the skills and ability to control it cannot influence the transaction process.Transactions Processing QualifiersIn order to qualify as a TPS, transactions made by the system must pass the ACID test. The ACID tests refers to the following four prerequisites: Atomicity Atomicity means that a transaction is either completed in full or not at all. For example, if funds are transferred from one account to another, this only counts as a bone fide transaction if both the withdrawal and deposit take place. If one account is debited and the other is not credited, it does not qualify as a transaction. TPS systems ensure that transactions take place in their entirety.Consistency TPS systems exist within a set of operating rules (or integrity constraints). If an integrity constraint states that all transactions in a database must have a positive value, any transaction with a negative value would be refused.Isolation Transactions must appear to take place in isolation. For example, when a fund transfer is made between two accounts the debiting of one and the crediting of another must appear to take place simultaneously. The funds cannot be credited to an account before they are debited from another.Durability Once transactions are completed they cannot be undone. To ensure that this is the case even if the TPS suffers failure, a log will be created to document all completed transactions. These four conditions ensure that TPS systems carry out their transactions in a methodical, standardised and reliable manner.Process of TPSThe six steps in processing a transaction are:Data entryData CaptureData validationProcessing and revalidationStorageOutput generationQuery supportData Entry To be processed, transaction data must first be entered into the system. There are a number of input devices for?entering data, including the keyboard and the mouse. Documents generated at the point where a transaction occurs are called source documents and become input data for?the system. For example, when a customer returns an item at a store, the sales receipt becomes the source document for the transaction "return item for?refund". The use of automated methods of data entry is known as source data automation.?Methods for Data Entry:Keyboard/video display terminalsOptical character recognition (OCR) devices, such as optical scanning wands and grocery check-out?scanners.Magnetic ink character recognition (MICR) devices, such as MICR reader/sorters used in banking for?checkOther technologies, including electronic mice, light pens, magnetic stripe cards, voice input, and tactile. Input also be used as input device depending upon the application requirementData CaptureWe could capture transaction data as close as possible to the source that generates the data. Salespersons capture data that rarely changes by prerecording it on machine-readable media, or by storing it on the computer system.Tips for Data Capturing:Capture data directly without the use of data media by optical scanning of bar codes printed on product packaging. It ensures the accuracy and reliability of data by comparingData ValidationThere are two steps in validation: error detection and error correction,Error detection is performed by one set of control mechanism, and error correction is done by another. Some commonly used error detection procedures are checking the data for?appropriate font (text, numbers, etc), checking for aberrations (abnormalities) (values that are too low or too high), and checking for missing data, invalid data, and inconsistent data. Missing data refers to fields that are missing a mandated data value. For example, if the number of hours worked by a part-time employee is missing on a payroll form; that is a missing-data error.Invalid data is data that is outside the range. For example, if the number of hours worked by a part-time employee is 72hours per week instead of the 1120 hours, then we have invalid dataInconsistent data means that the same data item assumes different values indifferent places without a valid reason. For example, if payroll records show that an employee worked 25 hours per?day. Processing and RevalidationOnce the accuracy and reliability of the data are validated, the data are ready for processing. There are two ways to process the transactions: online and batch mode. Following methods are available for Data Processing Online transaction processing (OLTP) is the almost instantaneous processing of data. The term online means that the input device is directly linked to the TPS and therefore the data are processed as soon as it is entered into the system. Input device may be at a remote location and be linked to the system by networks or by telecommunications systems. Some examples of?online transaction processing are ATM transactions, student registration for?classes, flight reservations. Data StorageProcessed data must be carefully and properly stored for future use. Data storage is a critical consideration-for many organizations because the value and usefulness of data diminish if data are not properly stored. The next step in the processing of a transaction is to output the results of the transaction to the decision maker.Output GenerationOnce data has been input, validated, processed, revalidated and stored, the output can be communicated to decision makers in two ways:Documents and reports: Documents are a popular output method. They can be processed further, either?to generate additional information or to present the same information in a different format. Some examples of documents are invoices, pay checks, purchase, invoice, sales receipts, and job orders. A document is usually a record of one transaction, whereas a report is a summary of two or more transactions. For example, the manager of a retail store may receive an invoice (i.e., a document) from a supplier indicating the quantity and type of each item ordered and the total cost of the order. A report, on the other hand, may summarize all the invoices from a given supplier.Forms, screens or panels: Computer output need not always be presented in hard-copy form (such as reports, documents, and printouts), but can also appear on computer screens and panels. Such soft-copy presentations are known as forms.Query SupportThe last step in processing a transaction is querying the system. Query facilities allow users to process data and information that may otherwise not be readily available. For example, a sales manager may query the system for the number?of damaged items in a given store. Many transaction-processing systems allow you to use the Internet, intranets, extranets, and web browsers or database management query languages to make inquiries and receive responses concerning the results of transaction processing activity. Typically, responses are displayed in a variety of pre-specified formats or?screens. Examples of queries include:Checking on the status of a sales order?Checking on the balance in an accountChecking on the amount of stock in inventory Transaction processing systems are responsible for capturing, storing, and providing access to the basic data of the organization. The goal is to capture the transaction data as soon as possible. Common collection methods include:Point-of sale servicesProcess controlElectronic data interchangeElectronic commerce websites.Types of ProcessingWhile the transaction process must be standardised to maximise efficiency, every enterprise requires a tailored transaction process that aligns with its business strategies and processes. For this reason, there are two broad types of transaction:Batch ProcessingBatch processing is a resource-saving transaction type that stores data for processing at pre-defined times. Batch processing is useful for enterprises that need to process large amounts of data using limited resources.Examples of batch processing include credit card transactions, for which the transactions are processed monthly rather than in real time. Credit card transactions need only be processed once a month in order to produce a statement for the customer, so batch processing saves IT resources from having to process each transaction individually.Updating in a batchThis is used when transactions are recorded on paper (such as bills and invoices) or when it's being stored on a magnetic tape. Transactions will be collected and updated as a batch at when it's convenient or economical to process them. Historically, this was the most common method as the information technology did not exist to allow real-time processing.The two stages in batch processing are:Collecting and storage of the transaction data into a transaction file - this involves sorting the data into sequential order.Processing the data by updating the master file - which can be difficult, this may involve data additions, updates and deletions that may require to happen in a certain order. If an error occurs, then the entire batch fails.Updating in batch requires sequential access - since it uses a magnetic tape this is the only way to access data. A batch will start at the beginning of the tape, then reading it from the order it was stored; it's very time-consuming to locate specific transactions.The information technology used includes a secondary storage medium which can store large quantities of data inexpensively (thus the common choice of a magnetic tape). The software used to collect data does not have to be online - it doesn't even need a user interface.Real Time ProcessingIn many circumstances the primary factor is speed. For example, when a bank customer withdraws a sum of money from his or her account it is vital that the transaction be processed and the account balance updated as soon as possible, allowing both the bank and customer to keep track of funds.The following features are included in real time transaction processing systems:Good data placement: The database should be designed to access patterns of data from many simultaneous users.Short transactions: Short transactions enables quick processing. This avoids concurrency and paces the systems.Real-time backup: Backup should be scheduled between low times of activity to prevent lag of the server.High normalization: This lowers redundant information to increase the speed and improve concurrency, this also improves backups.Archiving of historical data: Uncommonly used data are moved into other databases or backed up tables. This keeps tables small and also improves backup times.Good hardware configuration: Hardware must be able to handle many users and provide quick response times.Updating in real-timeThis is the immediate processing of data. It provides instant confirmation of a transaction. This involves a large amount of users who are simultaneously performing transactions to change data. Because of advances in technology (such as the increase in the speed of data transmission and larger bandwidth), real-time updating is now possible.Steps in a real-time update involve the sending of a transaction data to an online database in a master file. The person providing information is usually able to help with error correction and receives confirmation of the transaction completion.Updating in real-time uses direct access of data. This occurs when data are accessed without accessing previous data items. The storage device stores data in a particular location based on a mathematical procedure. This will then be calculated to find an approximate location of the data. If data are not found at this location, it will search through successive locations until it's found.The information technology used could be a secondary storage medium that can store large amounts of data and provide quick access (thus the common choice of a magnetic disk). It requires a user-friendly interface as it's important for rapid response time.Reservation Systems Reservation systems are used for any type of business where a service or a product is set aside for a customer to use for a future time.Storage & Retrieval of Data The storage and retrieval of data must be accurate as it is used many times throughout the day. A database is a collection of data neatly organized, which stores the accounting and operational records in the database. Databases are always protective of their delicate data, so they usually have a restricted view of certain data. Databases are designed using hierarchical, network or relational structures; each structure is effective in its own sense.Hierarchical structure: organizes data in a series of levels, hence why it is called hierarchal. Its top to bottom like structure consists of nodes and branches; each child node has branches and is only linked to one higher level parent work structure: Similar to hierarchical, network structures also organizes data using nodes and branches. But, unlike hierarchical, each child node can be linked to multiple, higher parent nodes.Relational structure: Unlike network and hierarchical, a relational database organizes its data in a series of related tables. This gives flexibility as relationships between the tables are built. A hierarchical structure. A network structure. A relational structure.In a TPS, there are 5 different types of files. The TPS uses the files to store and organize its transaction data:Master file: Contains information about an organization’s business situation. Most transactions and databases are stored in the master file.Transaction file: It is the collection of transaction records. It helps to update the master file and also serves as audit trails and transaction history.Report file: Contains data that has been formatted for presentation to a user.Work file: Temporary files in the system used during the processing.Program file: Contains the instructions for the processing of data.Back up & RecoveryBack up processSince business organizations have become very dependent on TPSs, a breakdown in their TPS may stop the business' regular routines and thus stopping its operation for a certain amount of time. In order to prevent data loss and minimize disruptions when a TPS breaks down a well-designed backup and recovery procedure is put into use. The recovery process can rebuild the system when it goes down.Recovery processA TPS may fail for many reasons. These reasons could include a system failure, human errors, hardware failure, incorrect or invalid data, computer viruses, software application errors or natural or man-made disasters. As it's not possible to prevent all TPS failures, a TPS must be able to cope with failures. The TPS must be able to detect and correct errors when they occur. A TPS will go through a recovery of the database to cope when the system fails, it involves the backup, journal, checkpoint, and recovery manager:Journal: A journal maintains an audit trail of transactions and database changes. Transaction logs and Database change logs are used, a transaction log records all the essential data for each transactions, including data values, time of transaction and terminal number. A database change log contains before and after copies of records that have been modified by transactions.Checkpoint: The?purpose?of?checkpointing?is?to?provide?a?snapshot?of?the?data?within?the?database.?A checkpoint,?in general,?is?any?identifier?or?other?reference?that identifies at a point in time the state of the database. Modifications to database pages are performed in memory and are not necessarily written to disk after every update. Therefore,?periodically,?the?database?systemmust?perform?a?checkpoint?to?write?these?updates?which?are?held?in-memory to?the?storage disk.?Writing?these?updates?to storage disk creates?a?point?in?time?in?which?the?databasesystem?can?apply?changes?contained?in?a?transaction log?during?recovery after?an?unexpected shut?down?or?crash?of?the?database system.Recovery Manager: A recovery manager is a program which restores the database to a correct condition which can restart the transaction processing.Depending on how the system failed, there can be two different recovery procedures used. Generally, the procedures involve restoring data that has been collected from a backup device and then running the transaction processing again. Two types of recovery are backward recovery and forward recovery:Backward recovery: used to undo unwanted changes to the database. It reverses the changes made by transactions which have been aborted. It involves the logic of reprocessing each transaction, which is very time-consuming.Forward recovery: it starts with a backup copy of the database. The transaction will then reprocess according to the transaction journal that occurred between the time the backup was made and the present time. It's much faster and more accurate.Types of back-up proceduresThere are two main types of Back-up Procedures: Grandfather-father-son and Partial backups:Grandfather-father-sonThis procedure refers to at least three generations of backup master files. thus, the most recent backup is the son, the oldest backup is the grandfather. It's commonly used for a batch transaction processing system with a magnetic tape. If the system fails during a batch run, the master file is recreated by using the son backup and then restarting the batch. However if the son backup fails, is corrupted or destroyed, then the next generation up backup (father) is required. Likewise, if that fails, then the next generation up backup (grandfather) is required. Of course the older the generation, the more the data may be out of date. Organizations can have up to twenty generations of backup.Partial backupsThis only occurs when parts of the master file are backed up. The master file is usually backed up to magnetic tape at regular times, this could be daily, weekly or monthly. Completed transactions since the last backup are stored separately and are called journals, or journal files. The master file can be recreated from the journal files on the backup tape if the system is to fail.TPS V/s DSSIn theory, the relational model supports databases for both transaction processing and decision support. In reality, compromises must be made in the design of database management software to optimize often- conflicting design objectives. Transaction-processing databases are optimized for the insert, update, and delete operations used to capture data, whereas decision-support databases are optimized for query operations used to analyze the data. Data for decision-support systems is often captured by online transaction-processing systems and then loaded into a decision-support system.Transaction-processing databasesTransaction-processing systems are designed to capture information and to be updated quickly. They are constantly changing and are often online 24 hours a day. Examples of transaction-processing systems include order entry systems, scanner-based point-of-sale registers, automatic teller machines, and airline reservation applications. These systems provide operational support to a business and are used to run a business.Transaction-processing systems have the following characteristics: High transaction rate -To ensure high throughput, transactions are simple and touch as few tables as possible.Constant change -Transactions occur in large numbers, and their changes are largely uncontrolled and unpredictable, within the limits of the system.Join paths -Join paths can be random and cyclic, and they are interpreted at the time of the query.No redundancy -Redundant and aggregate data is avoided in order to ensure data integrity and reduce lockout contention.Relational integrity -The reliability of the data depends on transaction integrity. Relational integrity checks are too slow and require much structural complexity.Predictable SQL queries -To ensure consistent response time, SQL statements are simple, predefined, and carefully tested. Indexes are optimized for these statements but are otherwise avoided because they adversely affect update and insert performance.Recoverability -To ensure against data loss, two-phase commit and rollback mechanisms, continuous transaction logs, and mirrored disk technology are employed.These goals are achieved by database schemas with a high degree of normalization--schemas that contain large numbers of tables connected by complex join paths. Normalization provides fast transaction response time and a complex schema that is easily manipulated by the applications that use it, but difficult to understand by the people who need the data.Decision-support databases: Decision-support systems are designed to allow analysts to extract information quickly and easily. The data being analyzed is often historical: daily, weekly, and yearly results. Examples of decision-support systems include applications for analysis of sales revenue, marketing information, insurance claims, and catalog sales. A decision-support database within a single business can include data from beginning to end: from receipt of raw material at the manufacturing site, entering orders, tracking invoices, and monitoring database inventory to final consumer purchase. These systems are used to manage a business. They provide the information needed for business analysis and planning.Decision-support systems have the following characteristics: Understandability- Data structures must be readily understood by users, often requiring denormalization and precomputed aggregations (summary data).Relatively infrequent changes-Most changes to the database occur in a controlled manner when data is loaded at regular intervals.Join paths -Join paths are simple, noncyclic, and based on business relations. They are defined when the database is built.Relational integrity-Relational integrity, necessary to ensure correct results, is built into the database when the data is loaded or deleted.Unpredictable and complex SQL queries-SQL query statements submitted against the database vary considerably and unpredictably from query to query. They can contain long, complex SELECT statements that make comparisons or require sequential processing. These queries might reference many thousands, millions, or even billions of records in a database.Large result sets-Extensive and frequent browsing must be supported.Recoverability Regular backups, or snapshots, of the static database ensure against data loss.Referenceswiki/Transaction_processing_systemnotes/mis/tps.pdfbestpricecomputers.co.uk/.../transaction-processing-systems.htmweb.cs.wpi.edu/~gpollice/cs562-s05/TPS-1_990913.pdcs.sunysb.edu/~cse515/Fall07/slides/ch26.pptfClass notesAPPENDIX7 Two-Tiered Model of TPSDBMSdatabase servermachinepresentation applicationservices servicespresentation applicationservices services? ? ?client machinescommunication 9 Three-Tiered Model of TPSDBMSdatabase servermachinepresentationserver ? ? ?client machinescommunicationpresentationserverapplicationserverapplication servermachine ................
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