What is the Input/Output FILE Identification section?
//INPUT1 DD DSN=INFILE,DISP=SHR
//OUTPUT DD SYSOUT=A
The fields INPUT1 and OUTPUT1 must correspond to the name following the ASSIGN TO statement in the FILE-CONTROL section of the COBOL Program.
FILE-CONTROL.
SELECT INPUT-FILE ASSIGN TO INPUT1.
SELECT OUTPUT-FILE ASSIGN TO OUTPUT1.
DD Field stands for Data Definition. Its main task is to tell the MVS OS, the input files from which data is read, and output file, to which OUTPUT information is written.
//INPUT1 DD DSN=INFILE,DISP=SHR
...DSN : A file containing records in IBM Mainframes is called Dataset. Every dataset has a name ; DataSetName(DSN).
DSN = INFILE indicates that the input data will be read from the Dataset INFILE.
SYSOUT=A indicates that the output will be written to the default printer(Job Spool).
DISP=SHR says that Disposition is Shareable. This means, that the dataset INFILE is not reserved for exclusive use. Other Jobs /Users can use this dataset simultaneously.
Showing posts with label tutorials. Show all posts
Showing posts with label tutorials. Show all posts
Monday, April 6, 2009
What is a Mainframe Computer?
A Mainframe computer is used in large business organisations for processing huge volumes of data e.g. census(population count), consumer statistics, banks and other financial institutions. Mainframe computers are manufactured by the organisation International Business Machines (IBM).
Large international banks like American Express, Citibank have millions of account holders. Thus, they generate a lot of business data - Available Account Balance, Withdrawal, Deposits, Interest Accrued. To process such bulk data, generate the statement of accounts, mainframe computer systems are used.
A Mainframe computer system is not meant to run tasks or programs fast. Instead, a Mainframe computer has a huge throughput, capable of handling many jobs and have high reliability and availability. A mainframe computer system has a plethora of features that enable to keep it up and running for years together. The time for which a computer system is up is called uptime. Thus, Long Uptimes are a feature of Mainframe Computer Systems. Mainframe vendors take pride in saying and boasting about the long uptimes of their computer systems. Mainframe computer systems are characterised by Reliability, Availability and Serviceability (RAS). Reliability of a computer system means those features that help to avoid and detect faults. Availability is a measure of the percentage of timefor which the system is available during it entire lifetime. Serviceability means different methods that help in diagnosing the fault.
Large international banks like American Express, Citibank have millions of account holders. Thus, they generate a lot of business data - Available Account Balance, Withdrawal, Deposits, Interest Accrued. To process such bulk data, generate the statement of accounts, mainframe computer systems are used.
A Mainframe computer system is not meant to run tasks or programs fast. Instead, a Mainframe computer has a huge throughput, capable of handling many jobs and have high reliability and availability. A mainframe computer system has a plethora of features that enable to keep it up and running for years together. The time for which a computer system is up is called uptime. Thus, Long Uptimes are a feature of Mainframe Computer Systems. Mainframe vendors take pride in saying and boasting about the long uptimes of their computer systems. Mainframe computer systems are characterised by Reliability, Availability and Serviceability (RAS). Reliability of a computer system means those features that help to avoid and detect faults. Availability is a measure of the percentage of timefor which the system is available during it entire lifetime. Serviceability means different methods that help in diagnosing the fault.
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