A holding pattern is nothing more than a big oval formed in a race-track shape that is designed to keep an aircraft in a specified space for a specified amount of time. A holding pattern can be published on either airway charts or terminal charts or can be unpublished, and specified by the air traffic controller. Watch the video (from 1’49 »):

Air Traffic Control phraseology training

Russian Air Traffic Controllers at work

How do air traffic controllers direct flights?

21:26 20/10/2010 What is an air traffic controller’s job from taking off to landing?>>

Hudson river ditching – January 15, 2009

Thanks to both Pierre, and Xavier who shared this link, you can see how the events unfolded, and how – thanks to the pilot Chesley « Sully » Sullenberg, the flight officer Jeffrey Skiles, and the air traffic controller’s self-control – the flight 1549 passengers remained unscathed: (you can read the radiocommunication transcript in the bottom right corner of the video hereafter)