i received the following error when i tried to open the standby database in read mode after creating it.

alter database open read only
ERROR at line 1:
ORA-16004: backup database requires recovery
ORA-01152: file 1 was not restored from a sufficiently old backup

I repeated the steps for creating standby database thrice but got the same error everytime.

Before opening the database in read mode, i also noticed that the redo logs
have not been archived at the location of standby database specified by
log_archive_dest_2='service=stby' on primary database and standy_archive_dest on standby database.