Understanding the Object Access Method

The object access method (OAM) uses a class of data referred to as objects. An object is a named stream of bytes. The content, format, and structure of that byte stream are unknown to OAM. There are no restrictions on the data in an object. For example, an object can be a compressed scanned image or coded data. Objects are different from data sets handled by existing access methods. Objects can be physically stored on disk (Db2® or file system), in the cloud, on an optical disk, or on a physical or virtual tape volume. The following characteristics distinguish them from traditional data sets:

• No record orientation. There are no individual records within an object.
• Broad range of size. An object can contain 1 byte or up to 2000 MB (2,097,152,000 bytes) of data. The maximum object size for all levels and sublevels of the OAM storage hierarchy except the optical level is 2000 MB. The maximum object size for the optical level of the OAM storage hierarchy is 256M. See Updating the IEFSSNxx PARMLIB member.
• Volume. Objects are usually much smaller than data sets; however, they are more numerous and consume vast amounts of external storage.
• Varying access-time requirements. Reference patterns for objects change over time or cyclically, allowing less-critical objects to be placed on lower-cost slower devices or media.

This topic covers the following topics that are related to using OAM to manage objects.