ORA-00056

Error: ORA-00056: DDL lock on object 'string.string' is already held in an incompatible mode

Causa: The attempted lock is incompatible with the DDL lock already held on the object. This happens if you attempt to drop a table that has parse locks.

Acción: Before attempting to drop a table, check that it has no parse locks. Wait a few minutes before retrying the operation.