Exam+Review+Outline

=This is a summary of the posted notes - Good luck on the Final Everyone!=

OWNERS: Jason Rudolph and Steven Zakulec

 * Why Mainframes?**


 * Large scale transaction processing – thousands per second
 * support thousands of users and application program
 * Simultaneously accessing resources
 * terabytes of information in databases
 * large bandwidth communications


 * What would you title this chart?**


 * What is a mainframe?**


 * a specialized computing system that provides greater security and availability than can be found on smaller machines
 * used for anything that requires high degrees of security and availability
 * provides lots of computing power and lots of capacity


 * What is a dataset?**


 * on z/OS, files are called datasets
 * you must pre-allocate and pre-format data sets before they can be used
 * a dataset can be a source program, library of macros, file of data records used by a processing program
 * sequential or partitioned


 * How data is stored**


 * stored on Direct Access Storage Device
 * DASD
 * records can be stored directly or sequentially and retrieved the same way


 * EBCDIC**


 * ancient IBM mainframes
 * extended binary coded decimal interchange
 * 8-bit character set, same as ASCII
 * z/OS web servers serve ASCII


 * TSO**


 * Time Sharing Options/Extentions
 * single user login usability, most people use ISPF


 * ISPF**
 * Interactive System Productivity Facility
 * 2-Edit 3-Utilities 6-Command 13-SDSF


 * JCL Statements**
 * Job Control Language
 * job statement must be the first statement
 * then exec statement, IDs program or procedure to be executed
 * then DD statement – allocates datasets (required)
 * compile, link, and go IGYWCLG


 * VSAM**
 * Virtual Storage Access Method
 * indexed


 * Advantages and Limitations of VSAM**
 * Advantages:
 * Supports more data set types
 * simplifies record processing
 * supports a variety of I/O techniques
 * provides greater efficiency for the application program and for the overall environment


 * Disadvantages:
 * it's data sets must reside on DASD
 * they cannot be created on tape
 * non - human readable


 * Key Dataset Characteristics**
 * organized either sequential, relative, or indexed
 * access is sequential, random, or dynamic


 * ESDS**
 * Entry Sequenced Data Set
 * records are stored in the order they are written
 * retrieved by addressed access
 * byte addresses cannot be changed


 * Problems with sequential files**
 * easy to add records, but very difficult to delete or update records
 * the only way to delete the records is to create a new file without them


 * Sequential Data Set**
 * Disadvantages:
 * Slow, complicated to change
 * Advantages:
 * Fast, when hit rate is high
 * most storage efficient
 * simple organization
 * recovers spaces from deleted records


 * KSDS**
 * Key Sequenced Data Set
 * Stored in Key sequence and controlled by an index
 * access it dynamically
 * sequential is useful for retrieving records in sorted form
 * random is useful in online applications

I**ndexed File Organization**
 * A file that has two parts


 * Index component**
 * data component
 * you can call it an indexed file
 * in the index, each entry contains a key value and where the record is in the data component
 * you have to have at least one index called the primary key
 * the first index is called the primary index
 * no duplicate keys
 * primary index and primary keys are in sequence, so dynamic access is possible
 * we can do sequential or random access
 * records are written in the primary key sequence in the data component
 * this reduces actuator movement during sequential access
 * Records may not be added in their sequential locations


 * Indexed Data Set**


 * **Disadvantages:**
 * slowest, direct access organization
 * especially slow when adding or deleting records
 * not very storage efficient
 * must store
 * the indexed records
 * the alternate index records
 * the data records
 * and the alternate data record
 * **Advantages:**
 * Can use multiple alphanumeric keys
 * can have duplicate alternate keys
 * can be read sequentially on any of its keys
 * can partially recover space from deleted records


 * Transaction Processing**

if it's completed, then it's committed
 * What is a transaction?**
 * A set of actions that must all be completed or not completed
 * if it's not completed, it has to be rolled back to before the transaction started
 * Example


 * **Money Transfer**
 * you want to move money from a checking account to a savings account
 * both have to happen


 * Transactional Systems**
 * **Transaction must be able to pass the acid test**
 * **A: Atomicity – has to finish all the way or not at all**
 * **C: Consistency – has to remain consistent**
 * can't debit one amount and have a different amount credited for the account
 * **I: Isolation – each transaction must appear to occur before or after any other transaction**
 * **D: Durability – if the transaction completes successfully, the changes due to the transaction will survive any future failures**


 * OLTP**
 * On line Transaction Processing
 * Class of software that administers transaction related programs
 * software functions include:
 * managing the user interface
 * retrieving and modifying data
 * tracking data locations and uses
 * handling communications
 * providing support functions for resource definition and use
 * interfacing with security software

CICS
 * Customer Information Control System
 * on OLTP product family from IBM
 * transactional subsystem of z/OS which
 * runs on line applications
 * supports many users running the same applications
 * manages the sharing of resources
 * insures the integrity of data
 * prioritizes the execution of transactions
 * insures fast response time
 * A transaction manager
 * transaction monitor
 * application server
 * used extensively
 * Systems that benefit from CICS include:
 * bank ATM
 * transaction processing systems
 * on line library catalogs
 * airline reservation systems
 * CICS functions
 * transaction processing systems perform interactive electronic commerce from a network of terminals processing both inquires and updates to the data stored in databases
 * a general purpose data communication system that can support the development of transaction processing applications in an OS390 environment
 * operating systems are designed to make the best use of a computers resources, CICS helps by behaving as a middle layer separating on line application programs from other programs and handling their administration itself
 * CICS tasks**
 * CICS provides concurrent transaction processing
 * under CICS all users share application programs and data files
 * if one user updates a database, changes are available to everyone instantly
 * 8 Steps in processing a transaction
 * 1. entry a transaction ID enters the system
 * 2. Task creation – CICS creates a task to process the transaction
 * the task is no ready to be run
 * 3. Dispatch - CICS determines which of the ready tasks should be run next and dispatches that task to be started
 * 4. Execution – the task invokes the appropriate CICS program and runs
 * 5. Processing – when the invoked program calls CICS to perform a service on its behalf the task gives up control of the CPU and waits for the requested service to be completed
 * 6. Re-dispatch – after the requested service has been completed, the task is ready to run again and CICS dispatches it again
 * 7. Return – when all work required to process the transaction ID the program issues a return command to return control to CICS
 * 8. Termination – CICS removes the task from the system
 * CICS – data integrity**
 * CICS uses ACID!
 * Good Luck on the final **SPRING 2007**

STUDY GUIDE SALTZ EXAM OWNERS: Ryan Shoultes & Meghan Sands GOOD LUCK!!!!!!!!!! - A data set is a collection of logically related stored on one disk storage volume or a set of volumes. - Direct Access Storage Disk: magnetic tape volume, hard drive -You can store and retrieve records either directly or sequentially.  -    ASCII value but for cobol  -    TSO: native mode/ like DOS  -    ISPF: menu system/ simplified GUI  -    It’s Fast  -    These systems are sometimes referred to as    “ ** data intensive ** ” systems  -    LARGE VOLUMES OF STUFF • A ** sequential data set ** is a collection of records written and read in sequential order from beginning to end • A ** partitioned data set (PDS) ** is a collection of sequential data sets, called members. – Consists of a directory and one or more // members // – The // members // are sequential data sets – Also called a // library // • A ** VSAM data set ** ( // Virtual Storage Access Method) // provides more advanced capabilities in terms of storage and access Sequential: records organized serially Relative: relative record number based Indexed: index based organization Sequential: accessed in order, one-by-one Random: specify a key to get the data record Dynamic: can access sequentially or randomly – read the record into the input record buffer – transfer it to the output record buffer – write the data to the output file from the output record buffer - Records in a Sequential file can not be deleted or  updated “in situ” (unless the same size record). • ** Slow ** - when the hit rate is low. • ** Complicated to change ** (insert, delete, amend) • ** Fast ** - when the hit rate is high. • ** Most storage efficient **. • Simple organization. • Recovers space from deleted records. • ** Wasteful ** of storage if the file is only partially populated. • ** Cannot recover space ** from deleted records. • Only a ** single, numeric key ** allowed. • Keys must map on to the range of the Relative Record numbers. • ** Fastest ** Direct Access organization. • Very ** little storage overhead **. • Can be read sequentially. • ** Slowest ** Direct Access organization. • ** Especially slow ** when adding or deleting records. • ** Not very storage efficient **. Must store the Index records, the alternate Index records, the data records and the alternate data records. • Can use ** multiple, alphanumeric keys **. • Can have ** duplicate alternate keys **. • Can be ** read sequentially ** on any of its keys. • Can ** partially recover space ** from deleted records. • **//The advantages of VSAM are://** – VSAM supports more data set types – Simplifies record processing – Supports a variety of I/O techniques – Provides greater efficiency for the application programs and for the overall environment • **//The major limitation of VSAM is://** – Its data sets must reside on DASD. They cannot be created on tape. Life cycle of designing and developing an application to run on z/OS includes phases of: – Requirements gathering and analysis – Design – Development – Test and debugging – Production – Maintenance __ Analysis  ____ Design Build Test __ 15% 25% 25% 35% • Batch processing is used for programs that can be executed: – With minimal human interaction – At a scheduled time or on an as-needed basis. Online processing is used for programs that require: – Human interaction – Can not be a scheduled – Data is stored on tape – Transactions are submitted for overnight processing – User does not require access to the data • **Reasons for using online:** – Users require access to the data – Short response time required • A set of actions that must either all be   completed or non be completed. – If the transaction completed, the transaction is   “Committed” – If the transaction does not complete, all state must be “Rolled-back” to the state of the system prior to the transaction – ** A ** tomicity - the transaction must execute completely, or not at all – ** C ** onsistency - Resources must remain consistent (ex. Same amount of money debited and credited) – ** I ** solation - each transaction must appear to occur before or after any other transaction – ** D ** urability - If the transaction completes successfully, the state (changes due to the transaction) will survive any future failures “When two trains approach each other at a crossing, both shall come to a full stop and neither shall start up again until the other has gone.”
 * SPRING 2008 FINAL EXAM REVIEW**
 * // DATA SETS //**
 * // D.A.S.D //**
 * // EBCIDC //**
 * // ISPF vs. TSO //**
 * // WHY DO YOU USE COBOL? //**
 * // TYPES OF DATA SETS //**
 * // DATA ORGANIZATIONS OF EACH //**
 * // METHOD OF ACCESS OF EACH //**
 * // To transfer a record from an input file to an output file we //**
 * // will have to: //**
 * // WHAT IS WRONG WITH A SEQUENTIAL DATA SET? //**
 * // ADVANTAGES & DISADVANTAGES OF DATA SET TYPES //**
 * //__ Sequential Data Set __//**
 * // Disadvantages //**
 * // Advantages //**
 * //__ Relative Data Set __//**
 * // Disadvantages //**
 * // Advantages //**
 * //__ Indexed Data Set __//**
 * // Disadvantages //**
 * // Advantages //**
 * // PHASES OF THE SYSTEMS DEVELOPMENT LIFE CYCLE //**
 * // BATCH Vs. ONLINE //**
 * //__ Batch __//**
 * //__ Online __//**
 * //__ REASONS FOR USING BOTH __//**
 * • Reasons for using batch: **
 * //__ TRANSACTIONS __//**
 * What is a transaction? **
 * What test is a transaction required to pass? **
 * // DEADLOCK! //**

-When two or more processes are each waiting for another to release a resource, or more than two processes are waiting for resources in a [|circular chain] • An OLTP is a class of software that administers transaction-related programs. – Managing the user interface – Retrieving and modifying data – Tracking data locations and uses – Handling communications – Providing support functions for resource definition and use – Interfacing with security software • CICS is an OLTP product family from IBM. • Transactional subsystem of z/OS which: – Runs online applications – Supports many users running the same application(s) – Manages the sharing of resources – Ensures the integrity of data – Prioritizes the execution of transactions – Ensures fast response time > organized in a form for easy retrieval. > available to all application programs and users. > single database than in a collection of flat files. > to read, write, update, insert, or delete data can be restricted. > (sequentially or go directly to the desired data). > immediately available to other applications. Because the data > exists in only one place, data integrity is more easily ensured. ** The role of a DBMS is to provide: ** > multiple applications) to a single copy of the data > mechanism with ACID properties (ACID is an > acronym for atomicity, consistency, isolation, and > durability) so as to maintain integrity for all > updates > copy of the data
 * // OLTP: All about it //**
 * • OLTP software functions include: **
 * CICS: All About It **
 * C ** ustomer ** I ** nformation ** C ** ontrol ** S ** ystem
 * What is a database **
 * A Database is a collection of interrelated data items, stored once and
 * Store and control large amounts of data
 * If properly designed it provides a consistent view of the data
 * All entities have a relationship between them
 * Why use a database? **
 * Reduces programming effort
 * Easier to create and modify data (compared to individual files)
 * Only need to update one location - one copy of all information
 * What is a database management system (DBMS)? **
 * Provides a method of storing and using data in a database
 * "Nothing more than a computerized data-keeping system"
 * Several types that can be used on z/OS: inverted list, hierarchic, network, and relational
 * Why are DBMS useful? **
 * A database stores the data only once in one place and makes it
 * Data can also be backed up and recovered more easily in a
 * Databases provide security by limiting access to data. The ability
 * Database structures offer multiple strategies for data retrieval
 * Finally, an update performed on part of the database is
 * 1) Enable concurrent access (I.e. multiple users,
 * 1) Control concurrent access via a locking
 * 1) Reduce data redundancy by maintaining only one
 * 1) Automated rollback, restart and recovery
 * What is the role of a DBA (Database Administrator) **
 * Provides standards for databases
 * Determines rules for accessing data and monitors its security
 * Approves the use of any programs that access production databases
 * Controls database integrity & availability; monitors activities for backup and recover
 * Guides, reviews and approves database designs
 * What is DB2? **
 * Short for database 2
 * A relational database produced in 1982 by IBM, was one of the first dbms to use sql
 * Relational database has no or little redundancy in data so it can efficiently store large volumes of data
 * Significantly slower than ims or idms databases
 * What Is IMS (Information Management System) **
 * A hierarchal database produced by IBM in 1972
 * Originally designed for the Apollo space program
 * Hierarchal system contains redundancy in data but is extremely fast


 * Database Comparison **

– Data is relatively static (can not just "add a column") – Navigational : need to know the structure to get to the data – Faster & more efficient - once Segment Search Arguments (SSAs) are coded
 * Hierarchical (IMS): **

– Changeable info – Change in structure : no impact on existing application – Non-Navigational : no need to know the structure right data (just tablename and columnname(s))
 * Relational(DB2): **

A Sysplex is an instance of a computer system running on one or more physical computers. Sysplexes are often isolated to a single system, but [|Parallel Sysplex] technology allows multiple mainframes to act as one. Sysplexes can be broken down into [|LPARs], or logical partitions, each running a different [|operating system].  ß thanks wiki • ** Benefits of a Sysplex include: ** – Improved growth potential – Improved load balancing – Improved level of availability _ Large business problems that involve hundreds of end users, or deal with volumes of work that can be counted in millions of transactions per day. _ Work that consists of small work units, such as online transactions, or large work units that can be subdivided into smaller work units, such as queries. _ Concurrent applications on different systems that need to directly access and update a single database without jeopardizing data integrity and security. • ** A Sysplex Timer: ** • Synchronizes all member systems' clocks. • // Server Time Protocol (STP) replaced the Sysplex Timers in 2005 // • // While the Sysplex Timers are physically separate machines, // // STP is an integral feature within the mainframe itself.. //
 * Benefits Of Database On A Mainframe **
 * All data is kept on one system limiting io time
 * // PARALLEL PROCESSING //**
 * // SYSPLEX: Systems Complex //**
 * // What kind of work is a Sysplex good for? //**