[ASK] Preparing for big image printing..

I Need help!
I want to print a big picture, its about 200cm x 100 cm. I edit this picture in Photoshop cs3.
I want to know,, how dpi must i give to get the best result when i print it later? And, does the size of my canvas is 200cm x 100 cm. too?? Or i only need a canvas where that size is have same comparasion with the real size?? Example:
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Real size = 200 cm X 100 cm
Comparasion size = 20 cm X 10 cm
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Is it like that????
Help me please.......

It depends on what the eventual use of the picture will be. If for a trade show art, you can probably get away with a resolution of 100 ppi or less. If it is some document that will need to be viewed at a close range, you might need 300 ppi.

That said, Photoshop's main file format is limited to 30,000 pixels in any direction. This should allow you up to 380 ppi resolution, which is more than you will need for most applications.