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An access method is a software component, operating system service or network interface that handles the storage/retrieval and sending/receipt of data. Access methods provide an application programming interface (API) for programmers to perform these services, which rely on low-level, specialized instructions.
In the 1960s, access methods were introduced by IBM as part of the mainframe OS/360 to provide access to data stored on disks, magnetic tapes and other external storage devices. In non-mainframe operating systems, this function is handled by device drivers.
Techopedia Explains Access Method
Access methods provide a convenient service to programmers for managing data storage and transmission. While providing the programmer with flexibility, the abstraction hides the many details regarding low-level disk access and communication protocol operations.
Access methods include internal structures to organize data as data sets, system-provided programs or macros to define data sets, and utility programs for data set processing. Error detection and correction capabilities are also provided.
Storage-oriented access methods include:
- Basic direct access method (BDAM)
- Basic sequential access method (BSAM)
- Basic partitioned access method (BPAM)
- Queued sequential access method (QSAM)
- Indexed sequential access method (ISAM)
- Virtual storage access method (VSAM)
- Object access method (OAM)
Network-oriented access methods include:
- Basic telecommunications access method (BTAM)
- Queued teleprocessing access method (QTAM)
- Telecommunications access method (TCAM)
- Virtual telecommunications access method (VTAM)
- Channeled access method (CAM)
