Introducing the Object Access Method

This section provides a brief introduction to Object Access Method (OAM). For more information, see the z/OS DFSMS Object Access Method Application Programmer's Reference.

In OAM, an object is a stream of bytes with a name. The content, format, and structure of that byte stream are unknown to OAM. For example, an object could be a compressed scanned image, or coded data. There are no individual records within an object.

A collection is a group of objects that typically have similar performance, availability, backup, retention, and class transition characteristics. Every object must be assigned to a collection. Object names must be unique within a collection; the same object name can be used in different collections.

OAM is an access method of MVS⁄DFP, the base for DFSMS. OAM uses the SMS-supplied hierarchy definition and management parameters to place user-accessible objects anywhere in the storage hierarchy. The hierarchy consists of DASD, library-resident optical volumes, and shelf-resident optical volumes. The location of an object in the hierarchy is unknown to the user; device-dependent information (such as track size) is not required.

For each object, the user can specify:
Storage Class
The level of service for the object, independent of the physical device or medium containing the object
Management Class
Backup, retention, and class transition characteristics for the object

The storage class and management class may be overridden by your installation defaults.