Change SCHEMA in Stored Procedure

How do you change the SCHEMA name in a stored procedure? Below are snippet of my code. I try using ALTER SESSION SET, but having problems. What's the solution.

CREATE OR REPLACE PROCEDURE test (schema_name IN VARCHAR) AS

	/** Define variables **/
	CURSOR a IS
		SELECT	* FROM A;
BEGIN


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	ALTER SESSION SET current_schema = schema_name;


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