If you want to maintain Dataguard for disaster recovery you need to keep up Dataguard running state and Synchronized.
You can read other Oracle Dataguard monitoring scripts like following.
To see the status of the switchover and the role of database which is in Standby or Primary state, execute following script.
select switchover_status,database_role from v$database;
To see archive gap in dataguard, execute following script.
SELECT THREAD#, LOW_SEQUENCE#, HIGH_SEQUENCE# FROM V$ARCHIVE_GAP;
Below script provides information about approximate completion time of the recovery process
select to_char(start_time,'DD-MON-RR HH24:MI:SS') start_time,item,round(sofar/1024,2) "MB/Sec" from v$recovery_progress where (item='Active Apply Rate' or item='Average Apply Rate');