1. A memory having a read mode and a write mode, comprising: a plurality of sub-arrays comprised of intersecting rows and columns of memory cells; a plurality of sets of local data line pairs, each set of local data lines coupled to a corresponding sub-array for carrying data to and from selected columns of the particular sub-array to which the set of local data lines corresponds; block-select means, coupled to the plurality of sub-arrays, for enabling a particular sub-array as determined by a first set of address signals; a set of global data lines for carrying data which corresponds to the data carried by the set of local data lines which corresponds to the enabled sub-array; first sense amplifier means, coupled to the plurality of sets of local data line pairs and the set of global data line pairs, for coupling data between the set of global data lines and the set of local data lines which corresponds to the selected sub-array; a block of redundant columns; a redundant local data line pair for carrying data to and from the block of redundant columns; a redundant global data line pair for carrying data; second sense amplifier means, coupled to the block of redundant columns via the redundant local data line pair, for coupling data between the redundant global data line pair and the redundant local data line pair; detection means for detecting when a column in the block of redundant columns is to replace a column in one of the sub-arrays of the plurality of sub-arrays; multiplexer means, coupled to the detection means, the redundant global data line pair, and the set of global data line pairs, for outputting external data which corresponds to the data present on the redundant global data line when the memory is in the read mode and the detection means detects that a column in the block of redundant columns is to replace a column in one of the sub-arrays and for providing, onto the redundant global data line pair, external data which has been received when the memory is in the write mode and the detection means detects that a column in the block of redundant columns is to replace a column in one of the sub-arrays.