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Indexed Sequential Access Method (ISAM) 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 .
It is the opposite of random access, the ability to access an arbitrary element of a sequence as easily and efficiently as any other at any time. Sequential access is sometimes the only way of accessing the data, for example if it is on a tape. It may also be the access method of choice, for example if all that is wanted is to process a ...
DMSII provided an ISAM (indexed sequential access method) model for data access, transaction isolation and database-recovery capabilities. The database schema was written in the proprietary Data and Structure Definition Language (DASDL). The DASDL source code was compiled with a system utility into a file containing the metadata for the ...
Extensible Storage Engine (ESE), also known as JET Blue, is an ISAM (indexed sequential access method) data storage technology from Microsoft. ESE is the core of Microsoft Exchange Server, Active Directory, and Windows Search. It is also used by a number of Windows components including Windows Update client and Help and Support Center. Its ...
The key must be such that it uniquely identifies a record. If more than one index is present the other ones are called alternate indexes. The indexes are created with the file and maintained by the system. IBM supports indexed files with the Indexed Sequential Access Method on OS/360 and successors.
Queued sequential access method (QSAM) Queued indexed sequential access method (QISAM) Basic partitioned access method (BPAM) Basic direct access method (BDAM) Virtual storage access method (VSAM) Execute Channel Program (EXCP) Execute Channel Program in Real Storage (EXCPVR) In MVS, starting with OS/VS2 Release 2 and continuing through z/OS ...
This means that Btrieve only deals with the underlying record creation, data retrieval, record updating and data deletion primitives. Together with the MicroKernel Database Engine it uses ISAM, Indexed Sequential Access Method, as its underlying storage mechanism. Btrieve is essentially a database that uses keys and indexes to organise data ...
While backwards compatibility was maintained, the older access methods suffered from performance problems due to the address translation required for virtual storage. The KSDS organization was designed to replace ISAM, the Indexed Sequential Access Method. Changes in disk technology had meant that searching for data in ISAM data sets had become ...