Oracle Data Guard Role Change History

Oracle documentation lists oracle-data-guard-in-oracle-database-views. Having diagnostics pack purchased and available one may find information of role changes in data quard also from DBA_HIST_DATABASE_INSTANCE view. No need to grep alert log.

select instance_name
     , to_char(lead(startup_time)over(order by startup_time)-startup_time,'dd hh24:mi:ss') durat
     , case when lead(host_name)over(order by startup_time) != host_name then 'ROLECHANGE' end switc
     , host_name
     , i.* 
  from DBA_HIST_DATABASE_INSTANCE i
 order by i.startup_time desc
;