Determining class transition and backup requirements

If the object has not been marked for expiration, OSMC determines if a class transition is needed. When a class transition is indicated, OSMC invokes the ACS routines. These routines evaluate the object's class assignments and change them, if necessary. Next, OSMC performs any actions that an object's class assignments indicate:

OSMC checks the storage class to determine if the object should be placed at a different level of the object storage hierarchy.
OSMC checks the management class to set the next date on which management action (that is, expiration or class transition) is needed.
OSMC makes up to two backup copies of the object if the management class indicates that one or two backup copies are required, and the requested number of backup copies does not currently exist.

This situation can result from any of the following scenarios:

This storage management cycle is the first one for a new object.
An application change changes an object’s management class to one that requires backups.
A class transition changes an object’s management class to one that requires backups.
An application change occurs so that the object's management class requires two backup copies where currently only one backup copy exists.
A class transition occurs so that the object's management class requires two backup copies where currently only one backup copy exists.

For objects with a primary copy on disk, tape, or optical, OSMC performs the following actions:

OSMC makes backup copies according to the management class that is assigned to the object. Backup copies can be directed to an optical disk, tape volume, or both depending on the definitions that are associated with the Object backup storage groups specified in the CBROAMxx member of PARMLIB.
If the management class requires a single backup copy, OSMC directs the backup copy to the associated Object Backup storage group. This storage group can be located on either an optical disk or a tape volume. If the management class indicates that two backup copies of the object are required and the SETOSMC statement associates two Object Backup storage groups with the Object storage group where the primary object copy resides, the first backup copy is written to one Object Backup storage group and the second backup copy is written to the other Object Backup storage group. These Object Backup storage groups can reside on the same or different media types (optical or tape).

For backup copies to be made to tape volumes, you must specify SETOAM statements with the STORAGEGROUP and TAPEUNITNAME parameters for the Object Backup storage groups.
The object is presented to the ACS routines in the CTRANS environment to allow for class transition.
If SETOSMC CLEAROLDLOC has been specified for objects transitioning from removable media to the DB2 sublevel or file system sublevel, the old location information is cleared during this OSMC cycle.
The next scheduled processing for the object is determined. If the object has not expired yet, OSMC processing for the object is next scheduled for when the object is to expire (based on the OSREQ STORE/CHANGE specifications for the RETPD and the management class assigned to the object).
On expiration of the object, OSMC deletes all copies of the object (primary and all the backups). Deletion removes information from the object directory but might or might not result in physical deletion, depending on the type of media. OSMC does not physically delete object copies residing on tape and WORM media. For objects that reside on tape volumes, the number of logical kilobytes that are deleted from the volumes is incremented for each object deleted. Objects that reside on a file system will be physically deleted, but there is a time delay before such deletion.

Related reading: For more information on expiring objects, see Objects not selected for expiration processing by OSMC.