Creating the conversion environment for Unicode Services

The z/OS client or server uses Unicode Services to support data conversion on files in either EBCDIC or ASCII formats as well as other data formats that are defined with a CCSID. No setup is needed to begin using Unicode Services. As of Version 1 Release 7, z/OS ships with Unicode Services ready to use. See z/OS Unicode Services User's Guide and Reference (previously titled z/OS Support for Unicode: Using Unicode Services) for more information .

With the NFS version 4 protocol (NFSv4), metadata are transferred between the server and client in the UTF-8 data format (ASCII text is not transferred directly). The CCSID used by Unicode Services for UTF-8 is 1208.

The convserv attribute defines how data conversion is performed between CCSIDs by specifying the conversion technique-search-order which Unicode Services will use for specified srv_ccsid(x) and cln_ccsid(x) code pages. Technique consists of up to five technique-characters corresponding to the available techniques (R, E, C, L and M) used to define the technique search order for Unicode Services to process the specified code pages.

The technique-characters, with description, are defined as follows. See z/OS Unicode Services User's Guide and Reference (previously titled z/OS Support for Unicode: Using Unicode Services) for more information.

R: Roundtrip conversion
Roundtrip conversions between two CCSIDs assure that all characters making the "roundtrip" arrive as they were originally.
E: Enforced Subset conversion
Enforced Subset conversions map only those characters from one CCSID to another that have a corresponding character in the second CCSID. All other characters are replaced by a substitution character.
C: Customized conversion
Customized conversions use conversion tables that have been created to address some special requirements.
L: Language Environment-Behavior conversion
Language Environment-Behavior conversions use tables that map characters like the iconv() function of the Language Environment Runtime library.
M: Modified Language Environment-Behavior conversion
Modified Language Environment-Behavior conversions use tables that map characters like the iconv() function of the Language Environment Runtime library does for converters ending with "C" (for example IBM-932C).

For mixed data format conversion, it is advisable to use more than one technique-character as one of the sub-conversions might exist only in round-trip mode and one only in enforced-subset. In the case of NFSv4, a technique-search-order of convserv(RE) or convserv(ER) would be required. In contrast, in the case of NFSv2 or NFSv3, convserv(R) would be sufficient for the data conversion.

The convserv attribute uses a default value of "LRE" which is recommended to provide correct translation of EBCDIC-newline to ASCII and back.