You should always monitor dataguard status if it is running or not syncronized or not. I will share with you the most used dataguard or standby monitor scripts.
If you don’t know What is Oracle dataguard or want to know more detail, you can read following article.
If you want to learn which of database is Standby and which of database is Primary, you can execute below query.
SELECT database_role, open_mode FROM v$database;
You can display the status of background processes in a standby database with below script.
select process, client_process,thread#,sequence#,status from v$managed_standby;
You can just want to see MRP process status then you can execute below script.
select process, client_process,thread#,sequence#,status from v$managed_standby where process like '%MRP%';
You can read other Oracle Dataguard monitoring scripts like following.