Is the margin for a future contract fixed after I initiate it?

I’m new to futures trading, and I have a question regarding the margin and how it works.

Suppose I buy a future contract with a margin requirement of Rs. 100 at the time of purchase and the margin increases to Rs. 150 after a period of time.

Now am I required to maintain Rs. 150 in my account to satisfy the margin requirement or am I only obligated to maintain the original requirement of Rs. 100?

increase of margin req is usually from:
span (increased expected volatility) or negative mtm

both cases, you’ll have to maintain increased margin to hold the position. If not, you’ll incur a penalty on a daily basis. If loss is beyond a certain threshold and margin is not maintained, broker has the right to square off your position.