Note that 802.3ah recommends using default Target SNR Margin of 5dB for 2BASE-TL ports and 6dB for 10PASS-TS ports in order to achieve mean Bit Error Rate (BER) of 10^-7 at the PMA service interface. This object is read-write for the -O subtype EFMCu ports (2BaseTL-O/10PassTS-O) and not available for the -R subtypes. Changing of the Target SNR Margin MUST be performed when the link is Down. Attempts to change this object MUST be rejected with the error inconsistentValue, if the link is Up or Initializing. Note that current SNR Margin of the PMEs comprising the EFMCu port is represented by efmCuPmeSnrMgn. This object MUST be maintained in a persistent manner.