----primary----
SQL> select group#,member,type from v$logfile where type='STANDBY';

----standby----
show parameter log_archive_dest_2

----compare primary and standby temp files----
SQL> select file_name,bytes/1024/1024 "SizeMB",maxbytes/1024/1024 "MaxSize MB",autoextensible from dba_temp_files;
----alternatively on 12C SQL>select name, bytes, create_bytes from v$tempfile;
ERROR at line 1:
ORA-01219: database or pluggable database not open: queries allowed on fixed tab
les or views only

----check primary and standby----
SQL> select name from v$datafile where status='OFFLINE';


----check primary and standby----
SQL> select db_unique_name, status, protection_mode, synchronization_status, synchronized from v$archive_dest_status where dest_id=2;
--In the previous output, you can ignore the synchronization status "CHECK CONFIGURATION" if the database is in Maximum Performance mode. 
--If theconfiguration is either "Maximum Protection or Availability", the status OK will be returned when there are no synchronization issues.

----Primary----
SQL> select thread#,max(sequence#) from v$archived_log group by thread#;

----Standby----
SQL> select thread#,max(sequence#) from v$archived_log where applied='YES' group by thread#;

----Standby----
SQL> select thread#,sequence#,process,status,client_process from v$managed_standby where thread#=1;

----Standby----
SQL> select name,value,time_computed from v$dataguard_stats;
SQL> !date

no backup running
blackout database monitoring

----primary----
--Set the JOB_QUEUE_PROCESSES parameter value to 0 so that no more jobs will be started. After the completion of switchover, reset it with the previous value.
select name, value from v$parameter where name = 'job_queue_processes';
SQL> alter system set JOB_QUEUE_PROCESSES=0 scope=both sid='*';

----If the primary database is RAC, ensure all the remaining primary instances except one are shut down. 
----If Active Data Guard is in use, disable it and ensure that all standby instances are in the mount state.
----It's advisable to take a full backup of the database either from primary or standby.
