[Zope] ZEO-Client

Hi, i' am using Zope-2.7.3 and i wan't my client-storages to be connected at zope-startup. In Zope-2.6.3 i used "open_at_startup" in DBTab but this option seems not to be included in release 2.7.3, however i can't find it in component.xml. If i add it to zope.conf anyway i get an exception. Any suggestions? Ralph