Forum OpenACS Development: How to set the table access permission for an open ACS user

Hi,
  I want to give access permission for the viewing or updating or inserting or deleting records into the table which was created by the openACS administrator in PostgreSQL for the users sake. plz tell me the method how to set the permissions for a table access and how to restrict the users for not doing any unauthorised access to the tables.
    Plz give me the code samples for this mechanism.

D.Venu Madhav.