Hey DSM,
Sure, so we explained it in a previous post and I'll give you an example: When you place a market order for a product, the RMS system blocks it based on the price of the best bid or ask. A trader places a buy market order for 1000 shares on a stock where best price is Rs. 100. However, quantity shown is only, say 25 since it is illiquid. What happens is that RMS will block an amount of 1000 * 100 = Rs. 1,00,000. In reality, 1000 shares are not available at Rs. 100. It could be that the other 9900 shares are spread out at an average price of Rs. 125. Or worse, maybe there is only a total of 200 shares available in the book in all.
Presently, the RMS is not doing these checks and lets the trader place the order as long as he has Rs. 1,00,000 available in his account. If after execution, the value is actually Rs. 1,50,00 then you will hit margin limits and maybe MtoM limits also. This can be a problem if broker/trader has to square off right away and someone is responsible for the losses. That is the present issue.
Now to mitigate this, you can place a limit order at a very high price to imitate a market order. This way, RMS blocks the right amount. Other way is to make RMS smarter and allow market orders but prevent the above scenarios which put both broker and trader at risk. The second scenario (a "protected" market order) is what we are working on rolling out soon.
Just a few days ago, we had someone punch in a market order for 5,500 lots of an illiquid option by accident. While the best buy price was within his RMS limits, it barely had any quantity and the 2nd - 5th level were extremely far off and thin in quantity.
Also, it's not possible to allow/disallow market orders on certain products (like allow on Nifty and other liquid products etc..) in the current RMS. Else, that would have been put in place since 80% of the trading happens on 20% of the products.
I hope that helps. If anything is confusing, do let us know. It is not something we are trying to hide, but something we are actively working on improving. We understand that during high volatile times you don't want to spend time punching in a limit order price.