ORA-26040: Data block was loaded using the NOLOGGING option

Issue:- When you try to open the standby in readonly and query a table, you will receive this error
Since some of the tables are set as no logging in primary side the blocks that changed with this tables have not generated any redo and hence this caused no changed applied to standby side.

Solution:-
	1. Recreate standby
	2. Perform rollforward recovery (if you see 

Permanent Solution
	1. As we cannot check each table logging or nologging
	select table_name,logging from dba_tables table_name='';
	table_name	logging
	----------	-------
	xxxx		NO

Put the primary database in force logging mode which is a first step while creating standby

	1. alter database force logging;