DNA consists of two strands of nucleic acid chains coiled around each other in the form of a double helix.The base of one strand of DNA are paired with bases on other strand by means of hydrogen bonding.

This hydrogen bonding is very specific as the bases can only base pair in a complementary manner. Adenine pairs with only thymine via 2 hydogen bonds and guanine pairs with cytosine through 3 hydrogen bonds.

Thus, the two strands of DNA are complementary to each other in the sense that the sequence of bases in one strand automatically determines that of the other. 

So the DNA stands cannot be identical, but they are complementary to each other.