CALCULATE STANDBY REDOLOG TO BE ADDED IN STANDBY DB

Formula to get the number of standby redologs on standby database.

STANDBY REDOLOGS TO BE ADDED = ( number of redolog group * number of threads in primary ) +1

Count the number of redolog groups on physical standby database

SQL> select count(group#) as NUMBER_OF_GROUPS from v$log;

NUMBER_OF_GROUPS
----------------
               3

Count number of threads on physical standby. If it is RAC ,more than one thread will be present

SQL> select count(thread#) from v$thread;

COUNT(THREAD#)
--------------
             1

Using the above two values ,lets substitute to find the number of standby redologs in formula

SQL> select (3*1)+1 as standbylog_count from dual;

STANDBYLOG_COUNT
----------------
               4

We got value as 4 which means ,we should add 4 redologs on standby database