Ok To Board (OTB) is an airline requirement. Traveling to Dubai your PNR must be marked with OK to board from respective airline.
“OK to Board” approval is only required for Indian citizens, Sri Lanka, Bangladesh or Pakistan who are traveling from their respective country of citizenship.
Due to an expansion in fake visas to UAE, many Indian passengers were deported back in the past. In order to control the fake visa issuance; airlines and sponsors double check the UAE visa and air tickets before departure and after checking visa authenticity, airline update visa message in the respective PNR.
The Airline verifies the Visa and then updates an Ok To Board message against the PNR. Airlines generally will take at least 24-48 working hours to update PNR after issuance of VISA.
If your flight ticket is not showing an OK to Board than the airline has the authority to deny entry on the aircraft. Passenger has to pay any liabilities/cancellation cost if his entry is denied.