How many levels of nested units of work are possible? Can units of work be used in parallel?
There is no limit to the number of units of work that can be nested or used in parallel. When a nested unit of work is committed, nothing is changed on the database – instead, the parent unit of work is notified of the changes, and they will be made when the parent is committed. A possible application for nested units of work is a user interface “wizard” in which each page of the wizard could be a separate nested unit of work committed when the user clicks Next. At the last page of the wizard, clicking an OK button commits the parent unit of work, thereby committing all of the nested units of work. Clicking the Cancel button cancels the entire transaction. Units of work can also be used in parallel. Essentially, this means that multiple units of work can be acquired from a single TopLink Session, and used simultaneously.
