BUFFER
A temporary storage area used to hold the date to reduce the CPU search & fetch time.

CICS (Customer Information Control System)

A transaction server that runs primarily on IBM mainframe systems under their z/OS or z/VSE operating systems.

DASD (Direct Access Storage Device)
A form of magnetic disk storage historically used in the mainframe and minicomputer (mid-range) environments. A redundant array of independent disks redundant array of disks (RAID) is a form of DASD.

"Direct access" means that all data can be accessed directly — in a form of indexing also known as "random access" — as opposed to storage systems based on seeking sequentially through the data (e.g., tape drives).

DATABASE
A collection of records stored in a computer in a systematic way, such that a computer program can consult it to answer questions. For better retrieval and sorting, each record is usually organized as a set of data elements (facts). The items retrieved in answer to queries become information that can be used to make decisions that might otherwise be more difficult or impossible to make. The computer program used to manage and query a database is known as a database management system (DBMS).

DB2
IBM's flagship relational database management system; DB2 Universal Database (DB2 UDB).

EMULATOR
An Application program that acts as an interface between the Computer system and Mainframe system. It receives the information from PC as ASCII format and converts them into EBCDIC and vice versa.

ISAM (Index Sequential Access Method)
A file management system developed at IBM that allows records to be accessed either sequentially (in the order they were entered) or randomly (with an index). Each index defines a different ordering of the records. An employee database may have several indexes, based on the information being sought. For example, a name index may order employees alphabetically by last name, while a department index may order employees by their department. A key is specified in each index. For an alphabetical index of employee names, the last name field would be the key.

ISAM was developed prior to VSAM (Virtual Storage Access Method) and relational databases.

ISPF
An Interactive menu driven software used in mainframe environment to choose other applications and to type, edit & submit your programs.

JOB
Job is a collection of one or more programs submitted to mainframe as a single unit.

LANGUAGE ENVIRONMENT
A common run time environment implemented by IBM to communicate between programs written in different languages. Using LE, you can call a C++ function from a COBOL program.

MAINFRAME
Often colloquially referred to as big iron - are large computers used mainly by organizations whose mission critical applications are characterized by an extremely high level of data such as air traffic control, consumer statistics, ERP, and financial transaction processing.

MIP (Million Instructions per Second)
Instructions per second (IPS) is a measure of a computer's processor speed.

MSU (Million Service Units)
A measurement of the amount of processing work a computer can perform in one hour. The term is most commonly associated with IBM mainframes. Most mainframe software vendors charge by MSUs consumed ("workload-based charging") or by total MSU system capacity. Thus, while MSU is a somewhat artificial construction, it does have a direct financial implication.

MULTIPROCESSING
Sharing the execution process by interconnecting more than one microprocessor using tightly or loosely couples technology is called as Multi Processing.

MULTI THREADING
Executing more than one thread (part of a task) parallely using a single processor is called multithreading.

MVS (Multiple Virtual Storage)
The most commonly used operating system on the System/370 and System/390 IBM mainframe computers. MVS is a Virtual Storage technology in which RAM is divided in slots, where each slot is shared by one processor to make the entire virtual memory available to all users independent of others.

OBJECT ORIENTED PROGRAMMING
A computer programming technique in which the algorithm is implemented based on the objects instead of variable.

OLTP (Online Transaction Processing)
A form of transaction processing conducted via computer network. Some applications of OLTP include electronic banking, order processing, employee time clock systems, e-commerce, and eTrading.

In large applications, efficient OLTP may depend on sophisticated transaction management software (such as CICS) and/or database optimization tactics to facilitate the processing of large numbers of concurrent updates to an OLTP-oriented database.

ONLINE PROCESSING
Executing more than one jobs simultaneously by time sharing or multiprocessing is called as online processing.

PAGE
The amount of data transferred from Hard Disk to RAM in a single processor fetch.  (Usually 4KB or 32KB)

PARALLEL PROCESSING
Running more than one application / task concurrently / simultaneously is called as parallel processing.

PERFORMANCE TUNING
The process of modifying a system to improve its efficiency (optimizing). The system can be a single computer program, a collection of computers or even an application.

PRIORITY PROCESSING
Executing the programs based on a numeric value assigned by the programmer / system administrator.

PROCEDURAL PROGRAMMING
A computer programming technique in which the program is divided into modules like function or subroutine or procedure or subprograms.

RAID (Redundant Array of Independent Disks)
A system of using multiple hard drives for sharing or replicating data among the drives.

SIMULATOR
A computer system, which simulates EBCDIC as the primary collating sequence to establish the run time environment to install all mainframe products.

SQL (Structured Query Language)
The most popular computer language used to create, modify and retrieve data from relational database management systems.

STRUCTURED PROGRAMMING
A computer programming technique that follows a top down design approach with block oriented structures.

TERMINAL
The client machine of a mainframe is called as a terminal; it contains a Monitor and Keyboard with a connector.

TIMESHARING
Switching the processor between two ore more processes by sharing the CPU Time is called as timesharing.

VIRTUAL MEMORY
A feature of computer systems wherein "permanent" data storage is used to assist in the handling processing functions.

VSAM (Virtual Storage Access Method)
An IBM disk file storage scheme first used in the S/370 operating system and later used throughout the MVS architecture. VSAM comprises four access methods: Key Sequenced Data Sets (KSDS), Relative Record Data (RRDS), Entry Sequenced Data Set (ESDS), and Linear Data Set (LDS).

Both IMS/DB and DB2 are implemented on top of VSAM and use its underlying data structures.

VSAM TUNING
The process of modifying the VSAM file storage scheme and associated parameters to improve its overall efficiency (optimizing).