Virtual Storage Access Method (VSAM)[1] is an IBM direct-access storage device (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,[NB 2] VSAM comprises four[NB 2] data set organizations: key-sequenced (KSDS), relative record (RRDS), entry-sequenced (ESDS) and linear (LDS).[2] The KSDS, RRDS and ESDS organizations contain records, while the LDS organization (added later to VSAM) contains a sequence of pages with no intrinsic record structure, for use as a memory-mapped file.
^"New Life for Legacy Systems at LaBarge". Datamation. May 11, 2007.
comparable with the VirtualStorageAccessMethod (VSAM), which was at that time a new and supposedly converged accessmethod for disk storage. Originally, VTAM...
granularity or access granularity. One common method to address these limits is to use multiple levels of virtualization. In several storage systems deployed...
store. ISAM was replaced at IBM with a methodology called VSAM (virtualstorageaccessmethod). Still later, IBM developed SQL/DS and then Db2 which IBM promotes...
including virtual computer hardware platforms, storage devices, and computer network resources. Virtualization began in the 1960s, as a method of logically...
VM VirtualStorageAccessMethod (VSAM) – for IBM's z/OS and z/VSE mainframe operating systems Shared-disk file systems (also called shared-storage file...
A storage area network (SAN) or storage network is a computer network which provides access to consolidated, block-level data storage. SANs are primarily...
serves as a storage device for a file system. File systems such as tmpfs can store files in virtual memory. A virtual file system provides access to files...
several notable caveats. Access to physical system resources (such as the network access, display, keyboard, and disk storage) is generally managed at...
call stack (called a "Java Virtual Machine stack" for clarity), which stores frames. A new frame is created each time a method is called, and the frame...
Retrieved 2 October 2013. Introduction to IBM Direct-accessStorage Devices and Organization Methods. International Business Machines Corporation. 1966...
Secondary Index function. MSDBs do not support secondary indexing. VirtualStorage Option (VSO) DEDBs can replace MSDBs in modern IMS releases, so MSDBs...
overall memory capacity. On some systems, a request for virtualstorage may allocate a block of virtual addresses for which no page frames have been assigned...
size of the virtual address space beyond the available amount of RAM using paging or swapping to secondary storage. The quality of the virtual memory manager...
client device that is used to access it. Desktop virtualization can be used in conjunction with application virtualization and user profile management systems...
stored data, such as location, storage structure, API, access language, and storage technology. Virtualized Data Access – Connect to different data sources...
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