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Access Method
An access method is a function of a mainframe operating system that enables access to data on disk, tape or other external devices. Access methods were present in several mainframe operating systems since the late 1950s, under a variety of names; the name ''access method'' was introduced in 1963 in the IBM OS/360 operating system.M. A. Auslander, D. C. Larkin, A. L. Scherr: "The Evolution of the MVS Operating System", pages 478-479 Access methods provide an application programming interface (API) for programmers to transfer data to or from device, and could be compared to |
Direct Access Storage Device
A direct-access storage device (DASD) (pronounced ) is a secondary storage device in which "each physical record has a discrete location and a unique address". The term was coined by IBM to describe devices that allowed random access to data, the main examples being drum memory and hard disk drives. Later, optical disc drives and flash memory units are also classified as DASD. The term DASD contrasts with sequential access storage device such as a magnetic tape drive, and unit record equipment such as a punched card device. A record on a DASD can be accessed without having to read through intervening records from the current location, whereas reading anything other than the "next" record on tape or deck of cards requires skipping over intervening records, and requires a proportionally long time to access a distant point in a medium. Access methods for DASD include sequential, partitioned, indexed, and direct. The DASD storage class includes both fixed and removable media ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Object Access Method
Object access method (OAM) is an access method An access method is a function of a mainframe operating system that enables access to data on disk, tape or other external devices. Access methods were present in several mainframe operating systems since the late 1950s, under a variety of name ... under z/OS which is designed for the storage of large numbers of large files, such as images. It has a number of distinguishing features, e.g. compared to Virtual storage access method, VSAM: *OAM datasets do not have an internal record structure; they are accessed as binary data streams. *OAM datasets are not directly cataloged. Rather, they are stored into OAM collections, with only the OAM collection being cataloged. The reason for this is to prevent the catalog from being overloaded with large numbers of (e.g. image) files. OAM is used in conjunction with IBM Db2. An example use case for OAM would be storing medical images in a Db2 database running under z/OS. History OAM was creat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mainframe Computer
A mainframe computer, informally called a mainframe or big iron, is a computer used primarily by large organizations for critical applications like bulk data processing for tasks such as censuses, industry and consumer statistics, enterprise resource planning, and large-scale transaction processing. A mainframe computer is large but not as large as a supercomputer and has more processing power than some other classes of computers, such as minicomputers, servers, workstations, and personal computers. Most large-scale computer-system architectures were established in the 1960s, but they continue to evolve. Mainframe computers are often used as servers. The term ''mainframe'' was derived from the large cabinet, called a ''main frame'', that housed the central processing unit and main memory of early computers. Later, the term ''mainframe'' was used to distinguish high-end commercial computers from less powerful machines. Design Modern mainframe design is characterized less b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Basic Partitioned Access Method
In IBM mainframe operating systems, basic partitioned access method (BPAM) is an access method for libraries, called partitioned datasets (PDSes) in IBM terminology. BPAM is used in OS/360, OS/VS2, MVS, z/OS, and others. A PDS consists of members (internally identical to sequential data sets), registered in a list called the ''directory''. The combination of members and directory is a single dataset on disk. The directory contains a list of member's names (8 characters, padded on the right with blanks, as required) and member's addresses. Addresses are relative to the start of the dataset in order to allow the PDS to be moved to a different disk location. Partitioned datasets can store any type of data, but they are often used to store executable programs, or ''load modules'', sometimes called binaries in other systems. Other uses include system assembler macro definitions, job control procedures, and program source code. Application program interface BPAM provides an applicat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Tape Data Storage
Magnetic-tape data storage is a system for storing digital information on magnetic tape using digital recording. Tape was an important medium for primary data storage in early computers, typically using large open reels of IBM 7 track, 7-track, later 9-track tape, 9-track tape. Modern magnetic tape is most commonly packaged in cartridges and cassettes, such as the widely supported Linear Tape-Open (LTO) and IBM 3592 series. The device that performs the writing or reading of data is called a tape drive. Autoloader (data storage device), Autoloaders and tape library, tape libraries are often used to automate cartridge handling and exchange. Compatibility was important to enable transferring data. Tape data storage is now used more for system backup, data archive and data exchange. The low cost of tape has kept it viable for long-term storage and archive. Open reels Initially, magnetic tape for data storage was wound on reels. This standard for large computer systems persis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Block (data Storage)
In computing (specifically data transmission and data storage), a block, sometimes called a physical record, is a sequence of bytes or bits, usually containing some whole number of records, having a maximum length; a ''block size''. Data thus structured are said to be ''blocked''. The process of putting data into blocks is called ''blocking'', while ''deblocking'' is the process of extracting data from blocks. Blocked data is normally stored in a data buffer, and read or written a whole block at a time. Blocking reduces the overhead and speeds up the handling of the data stream. For some devices, such as magnetic tape and CKD disk devices, blocking reduces the amount of external storage required for the data. Blocking is almost universally employed when storing data to 9-track magnetic tape, NAND flash memory, and rotating media such as floppy disks, hard disks, and optical discs. Most file systems are based on a block device, which is a level of abstraction for the hardwar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Set (IBM Mainframe)
In the context of IBM mainframe computers in the S/360 line, a data set (IBM preferred) or dataset is a computer file having a record organization. Use of this term began with, e.g., DOS/360, OS/360, and is still used by their successors, including the current z/OS. Documentation for these systems historically preferred this term rather than ''file''. A data set is typically stored on a direct access storage device (DASD) or magnetic tape, however unit record devices, such as punch card readers, card punches, line printers and page printers can provide input/output (I/O) for a data set (file). Data sets are not unstructured streams of bytes, but rather are organized in various logical record and block structures determined by the DSORG (data set organization), RECFM (record format), and other parameters. These parameters are specified at the time of the data set allocation (creation), for example with Job Control Language DD statements. Within a running program they are stored ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Storage Record
In computer science{{citation needed, date=July 2016, a storage record is: * A group of related data, words, or fields treated as a meaningful unit; for instance, a Name, Address, and Telephone Number can be a "Personal Record". * A self-contained collection of information about a single object; a record is made up of a number of distinct items, called fields. * In IBM mainframes, a ''record'' is a basic unit of device-to-program data transfers. Mainframe files, properly called data sets, are traditionally structured collections of records, as opposed to modern byte stream access files. Records may have a fixed length or variable length. In Unix-like systems, a number of programs (for example, awk, join, and sort) are designed to process data consisting of records (called lines) each separated by newlines, where each record may contain a number of fields separated by spaces, commas, or some other character. See also * Block (data storage) * Object composition * Record (computer s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Distributed Data Management Architecture
Distributed Data Management Architecture (DDM) is IBM's open, published software architecture for creating, managing and accessing data on a remote computer. DDM was initially designed to support record-oriented files; it was extended to support hierarchical directories, stream-oriented files, queues, and system command processing; it was further extended to be the base of IBM's Distributed Relational Database Architecture (DRDA); and finally, it was extended to support data description and conversion. Defined in the period from 1980 to 1993, DDM specifies necessary components, messages, and protocols, all based on the principles of object-orientation. DDM is not, in itself, a piece of software; the implementation of DDM takes the form of client and server products. As an open architecture, products can implement subsets of DDM architecture and products can extend DDM to meet additional requirements. Taken together, DDM products implement a distributed file system. Distribu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OS/VS
OS/VS may refer to one of a number of IBM operating systems for System/370 and successors characterized by the use of virtual storage (VS): * IBM OS/VS1, successor to MFT II, 1972-1984 * IBM OS/VS2, successor to MVT, including: ** OS/VS2 version 1, also known as SVS (Single Virtual Storage), 1972-1974 ** OS/VS2 version 2, also known as MVS (Multiple Virtual Storage), 1974-1981 OS/VS1 had no follow-on systems. Successor operating systems of OS/VS2 dropped the "OS/VS" tag and became simply " MVS/SE", "MVS/SP", "MVS/XA", etc. See also * MVS Multiple Virtual Storage, more commonly called MVS, was the most commonly used operating system on the System/370 and System/390 IBM mainframe computers. IBM developed MVS, along with OS/VS1 and SVS, as a successor to OS/360. It is unrelated ... * OS/360 and successors {{Set index article IBM mainframe operating systems ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virtual Storage Access Method
Virtual Storage Access Method (VSAM) is an IBM DASD file storage access method, first used in the OS/VS1, OS/VS2 Release 1 (SVS) and Release 2 (MVS) operating systems, later used throughout the Multiple Virtual Storage (MVS) architecture and now in z/OS. Originally a record-oriented filesystem, VSAM comprises four data set ''organizations'': key-sequenced (KSDS), relative record (RRDS), entry-sequenced (ESDS) and linear (LDS). The KSDS, RRDS and ESDS organizations contain records, while the LDS organization (added later to VSAM) simply contains a sequence of pages with no intrinsic record structure, for use as a memory-mapped file. Overview An IBM ''Redbook'' named "VSAM PRIMER" (especially when used with the "Virtual Storage Access Method (VSAM) Options for Advanced Applications" manual) explains the concepts needed to make use of VSAM. IBM uses the term ''data set'' in official documentation as a synonym of ''file'', and ''direct access storage device'' (''DASD'') because it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
