Object access method is an access method

Access method

An access method is a function of a mainframe operating system that enables access to data on disk, tape or other external devices. They were introduced in 1963 in IBM OS/360 operating system...

 under z/OS

Z/OS

z/OS is a 64-bit operating system for mainframe computers, produced by IBM. It derives from and is the successor to OS/390, which in turn followed a string of MVS versions.Starting with earliest:*OS/VS2 Release 2 through Release 3.8...

 which is designed for the storage of large numbers of large files, such as images. It has a number of distinguishing features, e.g. compared to VSAM

Virtual storage access method

Virtual storage access method an IBM disk file storage access method, first used in the OS/VS1, OS/VS2 Release 1 and Release 2 operating systems, later used throughout the Multiple Virtual Storage architecture and now in z/OS...

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• OAM datasets do not have any record structure, they are binary streams
• OAM datasets are not directly catalogued. Rather, they are stored into OAM collections, with only the OAM collection being catalogued. The reason for this is to prevent the catalogue from being overloaded with large number of e.g. image files.

OAM is meant to be used in conjunction with DB2

IBM DB2

The IBM DB2 Enterprise Server Edition is a relational model database server developed by IBM. It primarily runs on Unix , Linux, IBM i , z/OS and Windows servers. DB2 also powers the different IBM InfoSphere Warehouse editions...

. An example use case for OAM would be storing medical images in a DB2 database running under z/OS.