108 IBM Content Manager OnDemand Guide
5.3  Object access method for z/OS
In this section, we provide an introduction to object access method (OAM) and show its 
relationship with Content Manager OnDemand in a z/OS environment. 
For more information about setting up OAM, see the following documentation:
/SM590000DFSMS Object Access Method Planning, Installation, and Storage Administration Guide 
for Object Support, SC35-0426 
/SM590000Chapter 3, “OAM and System Management Subsystem customization”, in Image and 
Workflow Library: Content Manager for ImagePlus on OS/390 Implementation and EIP, 
SG24-4055
OAM is a hierarchical data management system (disk → optical → tape) that is used for 
archive storage. 
OAM uses the OSREQ macro interface and uses DB2 both for its internal (indexing) tables 
and for online storage objects. OAM is the DFSMSdfp component that manages a class of 
data, which is called objects, in a z/OS environment. Objects are bit strings that are handled 
as one large byte string rather than processing them as records, as is done with datasets. 
The content of this byte string is not known to OAM. No restrictions exist on the data type of 
this object; it can be an image, compressed data, or coded data. 
How to handle this data is left up to the application. OAM handles an unlimited number of 
objects, which can be stored on magnetic disk, magnetic tape, or optical storage. Objects are 
different from datasets, which are handled by existing access methods. The following 
characteristics distinguish objects from traditional datasets:
/SM590000Lack of record orientation: No concept of individual records within an object exists.
/SM590000Broad range of size: An object might contain less than 1 KB or up to 256 MB of data.
/SM590000Volume: Objects are much smaller than datasets; however, they can use much more 
external storage, depending on the type of application that creates them, such as image 
applications.
/SM590000Access time requirements: Reference patterns for objects change over time, allowing less 
critical objects to be placed on lower-cost, slower devices or media.
Note: When you use OAM as the storage manager, Content Manager OnDemand can 
retrieve the stored object directly from disk, optical drive, or tape.