This read-write value, per its own description, has no effect on the actual hardware configuration and exists purely so a network management tool can record whether it configured this OC12 port as fractional, frac(1) the default, or clear(2). Admins (or more precisely, the management software they use) set it purely as a bookkeeping flag reflecting how the port was intended to be provisioned, without it actually changing the port's behavior. For example, a management tool that provisioned this OC12 port for clear-channel (unchannelized) operation would set this object to clear(2) purely as a record of that intent, since the object itself doesn't drive the hardware.