CREATE CONTEXT

Purpose

Use the CREATE CONTEXT statement to:

• Create a namespace for a context (a set of application-defined attributes that validates and secures an application)

• Associate the namespace with the externally created package that sets the context

You can use the DBMS_SESSION.SET_CONTEXT procedure in your designated package to set or reset the attributes of the context.

Prerequisites

To create a context namespace, you must have CREATE ANY CONTEXT system privilege.

Syntax

create_context::=

Description of the illustration create_context.gif

Semantics

OR REPLACE

Specify OR REPLACE to redefine an existing context namespace using a different package.

namespace

Specify the name of the context namespace to create or modify. Context namespaces are always stored in the schema SYS.

schema

Specify the schema owning package. If you omit schema, then Oracle Database uses the current schema.

package

Specify the PL/SQL package that sets or resets the context attributes under the namespace for a user session.

To provide some design flexibility, Oracle Database does not verify the existence of the schema or the validity of the package at the time you create the context.

INITIALIZED Clause

The INITIALIZED clause lets you specify an entity other than Oracle Database that can initialize the context namespace.

EXTERNALLY EXTERNALLY indicates that the namespace can be initialized using an OCI interface when establishing a session.

GLOBALLY GLOBALLY indicates that the namespace can be initialized by the LDAP directory when a global user connects to the database.

After the session is established, only the designated PL/SQL package can issue commands to write to any attributes inside the namespace.

ACCESSED GLOBALLY

This clause indicates that any application context set in namespace is accessible throughout the entire instance. This setting lets multiple sessions share application attributes.

Examples

Creating an Application Context: Example This example uses the PL/SQL package emp_mgmt, created in "Creating a Package: Example", which validates and secures the hr application. The following statement creates the context namespace hr_context and associates it with the package emp_mgmt:

CREATE CONTEXT hr_context USING emp_mgmt;

You can control data access based on this context using the SYS_CONTEXT function. For example, suppose your emp_mgmt package has defined an attribute new_empno as a particular employee identifier. You can secure the base table employees by creating a view that restricts access based on the value of new_empno, as follows:

CREATE VIEW hr_org_secure_view AS
   SELECT * FROM employees
   WHERE employee_id = SYS_CONTEXT('hr_context', 'new_empno');