You can use DBMS_SESSION to set preferences and security levels. This package runs with the privileges of the calling user, rather than the package owner SYS.

• CLEAR_CONTEXT : Clears the context, this procedure must be invoked directly or indirectly by the trusted package.
• CLEAR_ALL_CONTEXT : Clears all context information, this procedure must be invoked directly or indirectly by the trusted package.
• CLEAR_IDENTIFIER : Clears the identifier, this procedure is executable by public.
• CLOSE_DATA_BASE_LINK : Closes database link
• FREE_UNUSED_USER_MEMORY : Lets you reclaim unused memory after performing operations requiring large amounts of memory. This procedure should only be used in cases where memory is at a premium. It should be used infrequently and judiciously.
• IS_ROLE_ENABLED : Determines if the named role is enabled for the session.
• IS_SESSION_ALIVE : Determines if the specified session is active
• LIST_CONTEXT : Returns a list of active namespace and context for the current session
• MODIFY_PACKAGE_STATE : Performs actions on the session state of PL/SQL program units that are active in the session
• RESET_PACKAGE : Deinstantiates all packages in the session. RESET_PACKAGE only frees the memory, cursors, and package variables after the PL/SQL call that made the invocation finishes running.
• SET_CONTEXT : Sets or resets the value of a context attribute
• SET_IDENTIFIER : Sets the identifier
• SET_NLS : Sets Globalization Support (NLS)
• SET_ROLE : Sets role
• SET_SQL_TRACE : Turns tracing on or off
• SWITCH_CURRENT_CONSUMER_GROUP : Facilitates changing the current resource consumer group of a user's current session
• UNIQUE_SESSION_ID : Returns an identifier that is unique for all sessions currently connected to this database