Oracle Procedure to Enable/Disable all constraints
I recommend you put the code in an AUTHID CURRENT_USER package.  You can certainly pass a Boolean, but I think a Varchar2 makes the usage clear.  You should unit test this code, add documentation, formalize the error handling, include instrumentation, and probably modify the reporting method.  

CREATE OR REPLACE PACKAGE Maint AUTHID CURRENT_USER IS

Procedure ToggleConstraints (iNewStatus In Varchar2);

END;
/


CREATE OR REPLACE PACKAGE BODY Maint IS

Procedure ToggleConstraints (iNewStatus In Varchar2) Is
Begin
   If (UPPER(iNewStatus) NOT IN ('ENABLED','DISABLED')) Then
      Raise_Application_Error(-20001
         , 'Constraints can only be toggled to ENABLED OR DISABLED.');
   End If;

   For vConstraint In 
   (
       SELECT 'alter table ' || table_name      
         || DECODE(UPPER(iNewStatus), 'DISABLED',' disable',' enable')
         || ' constraint ' || constraint_name As Statement
       FROM user_constraints 
       WHERE constraint_type = 'R' 
       AND status = DECODE(UPPER(iNewStatus),'DISABLED','ENABLED','DISABLED')
   ) Loop
      DBMS_Output.Put_Line(vConstraint.Statement);
      execute immediate vConstraint.Statement;
   End loop;
End;


END;
/

Set serveroutput on size 1000000 format wrapped
EXECUTE Maint.ToggleConstraints(iNewStatus=&gt;'ENABLED');