From morning to till now future OI in banknifty has increased with increasing price.
It simply indicates that rather than shortcovering it's purely long buildup.
There are lots of shorts still stucked on lower level and they will try to cover it.
As we know expiry is popular for it's shortcovering and most probably we'll see shortcovering move in second half.
It doesn't mean you have to jump directly in long trade.
Wait for banknifty to break it's today's high then long Banknifty for 39100.