anchor.diff:  
   alter_cluster
       : ALTER CLUSTER  cluster_name 
  -           (physical_attributes_clause
  -           | SIZE size_clause
  -           | allocate_extent_clause
  -           | deallocate_unused_clause
  -           | (CACHE | NOCACHE)
  -           )+
  -          parallel_clause? 
  -          ';'
  +        ( physical_attributes_clause
  +        | SIZE size_clause
  +        | allocate_extent_clause
  +        | deallocate_unused_clause
  +        | cache_or_nocache
  +        )+
  +        parallel_clause? 
  +        ';'
  +    ;
  +
  +cache_or_nocache
  +    : CACHE
  +    | NOCACHE
       ;
   
   database_name
  
positive.code:     ;
  
  drop_logfile_clauses
      : DROP STANDBY? LOGFILE ((','? logfile_descriptor)+
                              | MEMBER (','? filename)+
                              )
      ;
  
  switch_logfile_clause
  
negative.code: 
  alter_database
      : ALTER DATABASE database_name?
         ( startup_clauses
         | recovery_clauses
         | database_file_clauses
         | logfile_clauses
  