The setting of this variable determines whether or not Vision indexed file data blocks (as opposed to key blocks) are held in the memory-resident disk buffers. When it is set to "1" (on, true, yes), both data blocks and key blocks use the buffers. When set to "0" (off, false, no), only key blocks use the buffers. Setting this value to "1" usually improves performance unless very few buffers are being used. Note that holding data blocks in the buffers slightly increases the chances of losing data if a file opened for MASS-UPDATE is not closed properly (power failure, etc.). The default setting of this variable is "1".