Assuming that FK table belongs to USERA, you need to do the following:
1. Login as USERB and create a synonym for FK table in USERB schema
CREATE SYNONYM {object_name} for USERA.{object_name}
2. Then login as USERA and Grant select, insert on FK_table to USERB. You need only select privileges on FK Table.
This way USERB has not only has access to the object but also has necessary privileges to select/insert data.
Another simpler way is to create PUBLIC synonyms for all the tables you are using in your application and grant all to public. Then you will not have a problem whatever the user you are logged in as.
[Edited by kris109 on 02-17-2002 at 10:59 AM]
Remember the Golden Rule - He who has the gold makes the rules!
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Kris109
Ph.D., OCP 8i, 9i, 10g, 11g DBA