Investors enjoyed their biggest gains since July 18 after the VN-Index opened up and closed at its high for the session, adding 7.88 points, or 1.3%, to 637.34 for a second day of gains. The broad-based rally was led by the Big 4 – VNM (+2.5%), VCB (+1.9%), GAS (+1.7%) and VIC (+1.8%).