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How do the CREATE_UCODE and CONVERT_UCODE options control unicode conversion in Data ONTAP releases?

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Applies to

  • Clustered Data ONTAP 8.3
  • Clustered Data ONTAP 8.2      
  • Clustered Data ONTAP 8  
  • Data ONTAP 8 7-Mode       


How do the CREATE_UCODE and CONVERT_UCODE options control unicode conversion in Data ONTAP releases?

Data ONTAP 7-Mode:

In Data ONTAP 7-Mode, the options convert_ucode and create_ucode has effect on NFSv3 only.
If create_unicode is set to on, NFSv3 creates directories in unicode format, else creates them in non-unicode format.
If convert_ucode is on, and if NFSv3 attempts to access a non-unicode directory, conversion happen before serving data.
If convert_ucode is set to off, then no conversion happens when NFSv3 access non-unicode directory.
NFSv4/CIFS will always create unicode directories and convert non-unicode directories to unicode irrespective of what is the value of these options.

Clustered Data ONTAP:

The option create_ucode:
In Clustered Data ONTAP, create_ucode is always set to on and all protocols creates (including NFSv3) directories in unicode format.
This option cannot be changed in Clustered Data ONTAP. This option is always set to on even when migration 7-Mode volume (even if the option was set to off in 7-Mode).
Natively created clustered Data ONTAP volumes will always have this option set to on.

The option convert_ucode:
In clustered Data ONTAP natively created volumes, convert_ucode is set to on.
However, when a volume is transitioned from Data ONTAP 7-Mode to clustered Data ONTAP, the value of option is preserved and carried from Data ONTAP 7-Mode to clustered Data ONTAP.

In clustered Data ONTAP 8.2.X and earlier, the behavior of both these create_ucode and  convert_ucode volume options are same as Data ONTAP 7-Mode.

In clustered Data ONTAP 8.3 and later, the behavior of create_ucode is same as that of Data ONTAP 7-Mode.

However, the behavior is different for the option convert_ucode.
In all earlier releases, the convert_ucode option is not applicable to NFSv4/CIFS; while in Data ONTAP 8.3 and later, is also applicable to NFSv4/CIFS.
If convert_ucode is  ON (enabled), all protocols convert non-unicode to unicode (irrespective of size of the directories).
If convert_ucode is OFF (disabled), NFSv3 will not attempt conversion. NFSv4/CIFS will convert if directory size is < 2 MB.
If the non-unicode directory size is > 2 MB, access will be prevented and an ems log wafl.dir.convert.denied.2big will be triggered.

The following table summarizes the behaviors:

Directory Conversion For convert_ucode option 

convert_ucode value Access Method 7-Mode CDOT 8.2 and below CDOT 8.3 and above
OFF NFSv3 No conversion No conversion No conversion
OFF ZAPI No conversion No conversion No conversion
OFF NFSv4/CIFS Conversion Conversion Conversion only happens if the
directory size is less than 2MiB.
For directories larger than 2MiB,
no conversion happens and error

*This 2MiB limit was increased to 100MiB from ONTAP version 9.5 and above. 
ON NFSv3 Conversion Conversion Conversion
ON ZAPI Conversion Conversion Conversion
ON NFSv4/CIFS Conversion Conversion Conversion

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