For a candidate preparing for a mainframe job with a skill set of COBOL,JCL, DB2, CICS, VSAM and so on, the first thing that comes to his/her mind is to get a list of frequently asked interview questions in his domain/skill set.
Apache Hadoop framework is a big buzz in the IT world. It provides a solution the big data is posing to the digital world. The framework allows for data analysis of large datasets which are distributed across clusters of computers by using a simple programming model.
Hadoop streaming is a generic API (Applicaiton Programming Interface) which makes it easier for programmers to write and run map reduce jobs with any kind of executables. Map programs and Reduce programs receive input data in STDIN and output data in STDOUT in the form of key value pairs.
Well BIG DATA is all what we are surrounded by in today’s world. The web and the mobile world is generating enormous amount of data. Facebook for instance according to some old figures generates approximately 500 TERA BYTE of data each day, YES each day 500 TB !!!
Hadoop is a big buzz in the IT world these days. Apache™ Hadoop® is an open source software framework for processing huge volumes (BIG DATA) of distributed data (HADOOP DISTRIBUTED FILE SYSTEM) using distributed processing capabilities (MAP REDUCE).
The framework supports distributed processing of large datasets distributed across clusters of computers (COMMODITY HARDWARE) using simple programming models.
DB2 is the short name used for DATABASE 2. It is relational database product developed by IBM. This relational database management system was released by IBM in 1983 for MVS operating system. A RDBMS system represents all information in the form of tables. A table is a two dimensional array with horizontal rows and vertical columns.
JCL (Job Control Lanugauge) is the name of a scripting language used on IBM mainframe operating systems (MVS, OS/390 and VSE) to instruct the operating system to allocate space resources and time required to execute a job on the mainframe computers.
The Following Section contains some Basic JCL Examples used in day to day by mainframe developers.
COBOL stands for COMMON BUSINESS ORIENTED LANGUAGE. It is one of the oldest programming language and still widely used in the field of finance industry, retail industry and other government organization. COBOL was developed in the year 1960 bythe CODASYL Committee (Conference on Data Systems Languages).
An AbEnd (abnormal end) is an exception condition which results in the abnormal termination of a program or software. Its is a common terminology used in the mainframe world where a JCL terminates with an error code.
Following section covers some common abends faced by mainframe developers
S0C1 Operation Exception
Cause Reading or writing unopened file, Missing DD card, Subscript Error
MVS (Multiple Virtual Storage) was the most commonly used operating systems developed by IBM for mainframe computers (System/370 & System/390). MVS and its successor systems are used by large organizations for running critical applications in the areas like banking, insurance, retail & health industry etc.
The following section contains various tips and tutorials on MVS, collected from books, internet and other sources like mainframe forums.