RMD is not a special transaction. It is the minimum amount you must withdraw over the year, based on your age and the size of the account. Suppose you have a 401k and your RMD is $5000. That could be satisfied by withdrawing $5000 all at once on December 29, but it would also be satisfied if you had withdrawn $500 per month for living expenses. If you need to know what your RMD is, there are charts and online tools to calculate it. (Also note that for a defined pension, the entire payment is considered an RMD.)
The only reason the RMD question is important, is that you can't rollover money to other retirement accounts until after you meet your RMD for the year. If you aren't doing those things, then it does not change or hurt your tax return to say that all your 1099-R is an RMD.
(Again, suppose your RMD from your IRA is $5000, and you also want to convert some of your IRA to a Roth IRA. You can only do the Roth conversion after you have withdrawn at least $5000 and paid the tax on it.)
