Virtual Storage Access Method

What does Virtual Storage Access Method mean?

A Virtual Storage Access Method (VSAM) is a hierarchical file access method for IBM mainframe computers. It provides efficient access to large amounts of Data stored on direct access storage devices such as disk or tape. VSAM is based on the concept of a virtual storage pool, which is a logical representation of the physical storage devices used by the system. This allows VSAM to present a unified View of data storage to applications, regardless of the actual physical location of the data.

VSAM data is organized into logical units called datasets. A dataset is a collection of related records, and it can be divided into smaller units called blocks. VSAM provides a variety of access methods to allow applications to retrieve and update data efficiently. These access methods include:

• Key-sequenced access: This access method allows applications to retrieve and update data based on a key value.
• Relative Record number access: This access method allows applications to retrieve and update data based on its relative position in the dataset.
• Direct access: This access method allows applications to retrieve and update data based on its physical location on the storage Device.

VSAM is an important storage technology in the mainframe environment. It is used by a wide variety of applications, including database management systems, transaction processing systems, and data warehousing applications.

Applications

VSAM is important in technology today for several reasons. First, it provides efficient access to large amounts of data. This makes it well-suited for applications that require fast and reliable access to data, such as database management systems and transaction processing systems.

Second, VSAM is a hierarchical file access method. This means that it can organize data into a hierarchical structure, which makes it easy to manage and access data. This hierarchical structure is also well-suited for applications that need to store data in a structured way, such as data warehousing applications.

Third, VSAM is a highly scalable technology. This means that it can be used to support applications that require access to large amounts of data. This scalability makes VSAM well-suited for applications that are used by a large number of users or that require access to large amounts of data.

History

VSAM was developed by IBM in the 1960s. It was originally designed to provide efficient access to large amounts of data on disk storage devices. VSAM has since been updated and enhanced to support new technologies, such as Solid-State Storage devices.

VSAM has been a widely used storage technology for decades. It is a mature and well-supported technology that is used by a wide variety of applications.