Because VSAM does not read ahead buffers for direct processing, only the minimum number of data buffers are needed. Only one data buffer is used for each access. If you specify more data buffers than the minimum, this has little beneficial effect.

When processing a data set directly, VSAM reads only one data control interval at a time. For output processing (PUT for update), VSAM immediately writes the updated control interval, if OPTCD=NSP is not specified in the RPL macro.