If the split takes place on December 10th before the market opens, you can buy shares until the market closes on the 9th to participate in the split. If on the 10th after the market closes, you can buy shares on the 10th any time until the market closes. The "record date" is something shareholders should really ignore. This has to do with the total shares authorized and issued.
Look at it this way: If only people who held shares on or before Nov 26th (record date) would participate in the 2:1 split, there would be no reason for _anyone_ to buy shares between Nov. 26 and Dec. 10. Why buy shares at, say 42 and have a cost basis of 42 when people who bought shares Nov. 25 at 42 now had a cost basis of 21 (due to the 2:1)??? If OZRK traded at 23 right after the split, the 42 people would *really* be in the hole whereas the 23 people would have a profit. Doesn't happen.