Diagnosis
You cannot change the business event in the past because there aredevelopment plans associated with it.

Procedure
Delete the development plan item from the individual development plan ofthe attendees booked for the event. After this, you will be able tochange the business event.
When you have done this, check the individual development plan of theattendees booked for the event.
Caution: If the development plan item already has current data in it,this data is from Training and Event Management (see the documentationfor the switch DPLAN SIMU in table T77S0; note 588403).
If you need a 049 relationship in addition, you must create this again.