During schema and configuration upgrade, the server is started 'in process' without any connection handlers and the changes are made using an internal connection to the server.  During configuration/schema updates:

- If an 'object class violation' occurs the modification is processed again with schema turned off.  This seems to be required for instance to change the port number since the value is always required to be part of the LDAP connection handler's configuration entry.

- If an 'attribute or value already exists' error is returned the situation is logged and processing continues.