How to implement Oracle user/role security with Access front end?

Question

Hi,
We have successfully migrated our Access database tables to Oracle 10g using SQL developer. We've recreated all the users and roles(i.e., access groups) in Oracle and granted rights to tables.
In the Access front end database, in the Database window we have saved linked Oracle tables which replaced the Access tables. The forms, reports, queries run fine with the linked Oracle tables. All the linked table use one ODBC DSN to the Oracle database with the same Oracle user id.
We need to be able to authenticate users into the Oracle database and RE-link the tables based on their own unique user id. By during so we can allow users to use the Oracle standard user id/role and system privileges to control select, update, ect. rights to the database.
I've been able to use the VB code within Access to logon into the database with a unique id, but I have not been able to find out how to RE-link the tables to the unique user id using VB. There should be some way to relink tables dynamically, based on users login into the Access front end.
I don't know a great deal about Access projects, but I do know with SQL server allows login into your Access project and link tables dynamically.
Can someone give me some assistance or point me in the right direction?
Thanks in advance,
Larry

Answer 1

We had one of our programmers here come up with a VB code solution for re-linking table within Access. However the relinking takes 3-4 minutes for 100+ tables.
In an effort to help you understand the situation better, I will attempt to elaborate on the problem:
We have an Access 2003 application which currently has a front end using Access(forms, reports, queries, & VB code) and a MS Access 2003 backend.
We have migrated the backend tables to Oracle. However, we still have a need to maintain the front end in Access, since we have over 60 forms, 40 reports, 200+ queries in Access. Its easy to understand, we have a significant investment in the front end(Obviously, the plan is to migrate the front end also at some future date).
In order to utilized the existing front end, we have to validate and modify the current front end connections to the new Oracle backend. One of the features of Access is that you can "link" tables and save the link for runtime. Each Access table can have its own link which is a separate ODBC/JET connection. As such, each separate link has its own userid/database information.
The other issue with using the Access front-end is that Access utilizes a workgroup file to implement user and group security. The workgroup file contains all the users and which groups the users belong to in Access. Then within Access, you allow users access to object(tables, queries, ect) by their userid and or group. When users open an Access database with Access security enabled, they are required to log into Access. The login is authenticated by the workgroup file. Once, logged into Access, users have rights to Access objects based on their rights granted to their userid and groups they belong. The problem here is that when you remove the linked Access tables and replace them with linked Oracle tables, Access has knowledge about Oracle table rights granted to users; nor would you expect it to.
The dilema is the disconnect between Access and the fact Oracle utilizes a similar but much more sophisticated security model. It creates users and roles(which are similar to Access groups), and again this is independent of Access security.
Our solution was to still use the Access workgroup file security along with the Oracle security model. By using the Access userid and then creating a similar Oracle userid with similar table rights granted in Access, you could apply security within Access and also with the Oracle database.
For example, a user BOB logs into Access via the workgroup file, using VB code, Access then establishes a Oracle connection logining into Oracle using the same unique userid BOB into Oracle.
After connecting and validating user BOB into Oracle, then the Access tables are relinked to Oracle using the user BOB userid and table rights.
This Oracle userid has been granted table rights specific for this userid.This allows the user BOB to use the Access application and still be authenticated into the Oracle database.
The problem with this solution is that the relinking of the saved Access tables takes 3-7 minutes for about 100+ tables. This is not acceptable for users each time they log into the application.
Our current alternative is to use one Oracle userid to login each user, and use Access form restrictions/security to allow/prevent users from updating/viewing data. Obviously, this is not the optimal solution in respect to security, but it at least allows us to control access to the data(via the forms) by using one logon required for each user, and quick startup time for the application.
I understand SQL server does a better job in integration, but we use Oracle which is what I am trying to work with.
Larry