nse_cm stands for NSE cash market. BO is the product type. So BO was blocked for this scrip for the day. On 9th October, DHFL was quite volatile, so this would have been an ad-hoc block by our Risk Management team.
Since #1 doesn't say that CO is allowed, there is no way to say. You'll have to check. There are 100s of rejection messages. Some of them are one-off, that are seen in circumstances that are out of the ordinary. You would have to read the message and figure out what the rejection is. The link I've given above covers the most occurring rejections, however, I don't think you'd be able to generalise these.
RMS:Blocked for nse_cm DHFL-EQ BO block type: NON-SQROFF
got the message on OCT 09 2018, 09:30:03