You can specify that all compiled objects of a particular class should be upgraded in one execution of dbcc upgrade_object; for example, you can upgrade all triggers by using the trigger keyword.
Even though you use only one dbcc command, the upgrade of each object is recorded in a separate transaction; the old row is deleted from sysprocedures and a new row is written. Therefore, if you run dbcc upgrade_object on a large number of compiled objects, your system may run out of log space.