User modification to tables on the Logical Standby has three possible settings:
You can check the mode using this query:
SELECT GUARD_STATUS FROM V$DATABASE;
If you try to insert data into a table and the mode is 'ALL' and you are not the SYS user you should get an error
If you want users to modify non-replicated standby tables then you need to change the mode from its default of 'ALL'.
You can use DBA_LOGSTDBY_SKIP to find non-replicated tables ( the ones with skip rules ).
If you create new objects consider a naming convention that allows you to easily see the write status.