On-Line Transaction Processing

On-Line Transaction Processing On-Line Processing Immediate processing as the events occur Show the current state of the business Transaction Unit of computations having ACID properties ACID properties Atomicity Consistency Isolation Durability

TP (transaction processing) Systems TP systems typically involve Operating systems Database management systems Data communications Programming languages Application development TP systems A set of software modules that ease and automate application programming, execution, and administration for online TP applications Best TP systems require the least amount of code to be written for application development ! Transaction processing is a prerequisite for mastering the complexity of distributed, heterogeneous system (J.Gray)

Transaction Processing Services ( in addition to, but incooperation with a DB system ) Manage Heterogeneity Presentation Service Control Communication Context Management Terminal Management Program Management Load Balancing Start / Restart

User’s / Programmer’s Views of a TP System (1/2) Each transaction is an independent unit of work that executes once and produces permanent result Transaction : the execution of a program that Gets a request from a terminal Performs the request by accessing a database and executing application programs Returns a response to the terminal

User’s / Programmer’s Views of a TP System (2/2) A simple TP application consists of A form and menu definitions Input data validation Mapping of request types into application program names Application programs to execute requests User Shared data Transaction Application Program File Manager ( or DBMS ) Read,Write Read … Start-trans Commit-trans Abort-trans Write User

Implementer’s (system’s) View of a TP System (1/2) A collection of various modules and resources On-line : user waits for response (seconds, not days) The bleeding edge 100,000 terminals 1,000 disks 3,000 transactions per second

Implementer’s (system’s) View of a TP System (2/2) TP SUB SYSTEM User Application Program Start_trans, Commit_trans, Abort_trans … User Transaction Manager Shared data Access Method Undo, Redo Recovery Manager Read_log Write_log Log Scheduler (Lock Manager) File Manager ( or DBMS ) Write_log Commit Manager

OLTP Applications Communications Travel Finance Manufacturing Setting up and billing for telephone calls, electronic mail, etc Travel Reservations and billing for airlines, cars, hotels, etc Finance Banking, stock trading, ATM, POS (point of sale) Manufacturing Order entry, job and inventory planning and scheduling, accounting Processing Control Control of factories, warehouses, plants, etc

Characteristics of OLTP Applications Large number of simple and pre-defined transacrions Predictable input Huge terminal users concurrently Fast response Large shared databases

Terminal-User Requirements High Performance Measured in transactions per second 90% of transactions get 2 second response time ! High Availability Can always run transactions (no downtime) Atomicity A virtual sequential transaction processor Persistence Never loses results of transactions

OLTP Monitor Coordinates the flow of requests between terminals and application programs that perform transactions Helps transaction application development Administration and management of a TP system Why TP Monitor ? Performance Ease of use

General Features of a TP Monitor Transaction Execution Scheduling Load balancing Failure isolation and recovery System Administration Authentication and authorization Status monitoring Performance tuning Application Development Forms editor / compiler Client / Server development tools