Groups can be contained within other groups, allowing for hierarchies of groups. 

All jobs must be assigned to a group (this is a change from adTempus 2.x, where the "root" group did not explicitly exist and jobs in the root did not have a group assignment). Beginning in 3.0, if the job is to be in the root group it must explicitly be assigned to that group. 

The Root group always has an OID of "{2C13CBB7-57D7-44A7-A74C-92B9F92A2A01}:{9A3EA996-9137-4EA7-8CAC-55E70695B473}".

All Groups descend from the Root group. The Root group cannot be deleted or renamed. 

When you create a new group, it must be assigned a parent group--either the Root or another existing group. 

When a group is deleted (using IADTIndependentObject::Delete), all of its child groups are deleted as well. The jobs in the group and its subgroups, however, are not deleted: they are removed from the group(s), so they are returned to the root level. 

To delete the jobs within the group, use DeleteMembers.