MacLochlainns Weblog

Looking through an error on the web, I notices that the solution is nested in Ask Tom. That’s true for so many solutions, but they likewise have long discussions like this one in the OraFAQ Forum.

It seems that most folks search on is the following. The problem appears to be linked to attempts to call the DBMS_SESSION.SET_CONTEXT directly in their code, instead of through a predefined procedure. The procedure is generally inside a security package in a security schema for reference.

BEGIN
*
ERROR at line 1:
ORA-01031: insufficient privileges
ORA-06512: at "SYS.DBMS_SESSION", line 94
ORA-06512: at line 2

I figured it might help to provide a simple example because I use VPDs in my second database class, and this is where some of my students get hung up. It strikes me others in the Oracle community may get stuck here too.

1. Create a user with necessary permissions as the SYSTEM user:

CREATE USER sample IDENTIFIED BY sample;
GRANT CREATE SESSION, CREATE ANY CONTEXT, CREATE ANY PROCEDURE TO sample;

2. Create the CONTEXT reference as the SAMPLE user, which uses a function to populate the CONTEXT.

CREATE OR REPLACE CONTEXT sample_ctx USING set_context;

3. Create the function as the SAMPLE user to set the context. The CONTEXT is a literal value inside the procedure with a name and value pair.

CREATE OR REPLACE PROCEDURE set_context
( pname  VARCHAR2
, pvalue VARCHAR2) IS
BEGIN
  -- Create a session with a previously defined context.
  DBMS_SESSION.SET_CONTEXT('SAMPLE_CTX',pname,pvalue);
END;
/

4. Set the local session sample_ctx CONTEXT as the SAMPLE user.

EXECUTE set_context('email','sherman@atlanta.org');

5. You now query the user-defined CONTEXT with case insensitive strings that match the CONTEXT and pname call parameter that you set it. The following shows that query against dual. You should note that it returns a case sensitive string of the pvalue call parameter.

SELECT sys_context('sample_ctx','email') FROM dual;

As always, I hope this helps somebody and saves them time.