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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'') bec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Datamation
''Datamation'' is a computer magazine that was published in print form in the United States between 1957 and 1998,Venerable IS Journal Shuts Down Sharon Machlis // ComputerWorld, page 15, 19 January 1998 and has since continued publication on the web. ''Datamation'' was previously owned by QuinStreet and acquired by TechnologyAdvice in 2020. Datamation is published as an online magazine at Datamation.com. History and profile When ''Datamation'' was first launched in 1957, it was not clear there would be a significant market for a computer magazine given how few[...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IBM Mainframe Utility Programs
This article discusses support programs included in or available for OS/360 and successors. IBM categorizes some of these programs as utilities and others as service aids; the boundaries are not always consistent or obvious. Many, but not all, of these programs match the types in utility software. The following lists describe programs associated with OS/360 and successors. No DOS, TPF or VM utilities are included. History/Common JCL Many of these programs were designed by IBM users, through the group SHARE, and then modified or extended by IBM from versions originally written by a user. These programs are usually invoked via Job Control Language (JCL). They tend to use common JCL DD identifiers (in the OS, now z/OS operating systems) for their data sets: Dataset utilities IDCAMS IDCAMS ("Access Method Services") generates and modifies Virtual Storage Access Method (VSAM) and Non-VSAM datasets. IDCAMS was introduced along with VSAM in OS/VS; the "Access Method" reference ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ISAM
ISAM (an acronym for indexed sequential access method) is a method for creating, maintaining, and manipulating computer files of data so that records can be retrieved sequentially or randomly by one or more keys. Indexes of key fields are maintained to achieve fast retrieval of required file records in Indexed files. IBM originally developed ISAM for mainframe computers, but implementations are available for most computer systems. The term ''ISAM'' is used for several related concepts: *The IBM ISAM product and the algorithm it employs. *A database system where an application developer directly uses an application programming interface to search indexes in order to locate records in data files. In contrast, a relational database uses a query optimizer which automatically selects indexes. *An indexing algorithm that allows both sequential and keyed access to data. Most databases use some variation of the B-tree for this purpose, although the original IBM ISAM and VSAM implementat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OS/360 And Successors
OS/360, officially known as IBM System/360 Operating System, is a discontinued batch processing operating system developed by IBM for their then-new System/360 mainframe computer, announced in 1964; it was influenced by the earlier IBSYS/IBJOB and Input/Output Control System (IOCS) packages for the IBM 7090/7094 and even more so by the PR155 Operating System for the IBM 1410/ 7010 processors. It was one of the earliestJust a few years after Atlas Supervisor, Burroughs MCP and GECOS operating systems to require the computer hardware to include at least one direct access storage device. Although OS/360 itself was discontinued, successor operating systems, including the virtual storage MVS and the 64-bit z/OS, are still run and maintain application-level compatibility with OS/360. Overview IBM announced three different levels of OS/360, generated from the same tapes and sharing most of their code. IBM eventually renamed these options and made some significant design ch ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DOS/360 And Successors
Disk Operating System/360, also DOS/360, or simply DOS, is the discontinued first member of a sequence of operating systems for IBM System/360, System/370 and later mainframes. It was announced by IBM on the last day of 1964, and it was first delivered in June 1966. In its time, DOS/360 was the most widely used operating system in the world. DOS versions BOS/360 The Basic Operating System(BOS) was an early version of DOS and TOS which could provide usable functionality on a system with as little as 8 KB of main storage and one 2311 disk drive. TOS/360 TOS/360 (Tape Operating System/360, not a DOS as such and not so called) was an IBM operating system for the System/360, used in the early days around 1965 to support the System/360 Model 30 and similar platforms. TOS, as per the "Tape" in the name, required a tape drive. It shared most of the code base and some manuals with IBM's DOS/360. TOS went through 14 releases, and was discontinued when disks such as the IBM ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virtual Memory
In computing, virtual memory, or virtual storage is a memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" which "creates the illusion to users of a very large (main) memory". The computer's operating system, using a combination of hardware and software, maps memory addresses used by a program, called '' virtual addresses'', into ''physical addresses'' in computer memory. Main storage, as seen by a process or task, appears as a contiguous address space or collection of contiguous segments. The operating system manages virtual address spaces and the assignment of real memory to virtual memory. Address translation hardware in the CPU, often referred to as a memory management unit (MMU), automatically translates virtual addresses to physical addresses. Software within the operating system may extend these capabilities, utilizing, e.g., disk storage, to provide a virtual address space that c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transactional VSAM
Transaction or transactional may refer to: Commerce *Financial transaction, an agreement, communication, or movement carried out between a buyer and a seller to exchange an asset for payment *Debits and credits in a Double-entry bookkeeping system *Electronic funds transfer, the electronic exchange or transfer of money from one account to another *Real estate transaction, the process whereby rights in a unit of property is transferred between two or more parties *Transaction cost, a cost incurred in making an economic exchange *Transactional law, the practice of law concerning business and commerce Computing *Transaction processing, information processing that is divided into individual, indivisible operations *Database transaction, a unit of work performed within a database management system *Atomic transaction, a series of database operations such that either all occur, or nothing occurs Other uses *Transactions, the published proceedings of a learned society: ** *Transaction ... [...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] |
B+ Tree
A B+ tree is an m-ary tree with a variable but often large number of children per node. A B+ tree consists of a root, internal nodes and leaves. The root may be either a leaf or a node with two or more children. A B+ tree can be viewed as a B-tree in which each node contains only keys (not key–value pairs), and to which an additional level is added at the bottom with linked leaves. The primary value of a B+ tree is in storing data for efficient retrieval in a block-oriented storage context — in particular, filesystems. This is primarily because unlike binary search trees, B+ trees have very high fanout (number of pointers to child nodes in a node, typically on the order of 100 or more), which reduces the number of I/O operations required to find an element in the tree. History There is no single paper introducing the B+ tree concept. Instead, the notion of maintaining all data in leaf nodes is repeatedly brought up as an interesting variant. Douglas Comer notes in an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Structure
In computer science, a data structure is a data organization, management, and storage format that is usually chosen for Efficiency, efficient Data access, access to data. More precisely, a data structure is a collection of data values, the relationships among them, and the functions or operations that can be applied to the data, i.e., it is an algebraic structure about data. Usage Data structures serve as the basis for abstract data types (ADT). The ADT defines the logical form of the data type. The data structure implements the physical form of the data type. Different types of data structures are suited to different kinds of applications, and some are highly specialized to specific tasks. For example, Relational database, relational databases commonly use B-tree indexes for data retrieval, while compiler Implementation, implementations usually use hash tables to look up identifiers. Data structures provide a means to manage large amounts of data efficiently for uses such a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IBM Db2
Db2 is a family of data management products, including database servers, developed by IBM. It initially supported the relational model, but was extended to support object–relational features and non-relational structures like JSON and XML. The brand name was originally styled as DB/2, then DB2 until 2017 and finally changed to its present form. History Unlike other database vendors, IBM previously produced a platform-specific Db2 product for each of its major operating systems. However, in the 1990s IBM changed track and produced a Db2 common product, designed with a mostly common code base for L-U-W (Linux-Unix-Windows); DB2 for System z and DB2 for IBM i are different. As a result, they use different drivers. DB2 traces its roots back to the beginning of the 1970s when Edgar F. Codd, a researcher working for IBM, described the theory of relational databases, and in June 1970 published the model for data manipulation. In 1974, the IBM San Jose Research center dev ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
