Rebuild Standby database using incremental backup in case if its lagging:

 

1- Take the current scn from the standby database:

SQL> select  

current_scn

from

v$database;

 

CURRENT_SCN

-----------

     255263

2- Take incremental from the target SCN 255263:

RMAN> backup incremental from scn 485263 database format '/u02/inc_backup_%U';

3- Move the backup pieces to standby server and register it:

RMAN> catalog start with '/u02/';

4- Rolling forward the generated backup:

recover database noredo;