These recommendations are useful when writing globalized applications.
- Because the system is included with a default CCSID of 65535, character
data conversions do not normally occur in applications. You should look over
the CCSID information in this topic, however, because the system might need
to participate in a multilingual environment, a network, or exchanging data
at a later time.
- Applications implementing their own mapping scheme should use CCSID 65535,
where a CCSID assignment is necessary. For example, depending on what an application
does, it might need to use CCSID 65535 for the files, or it might need to
use CCSID 65535 for the jobs. Because other applications may require CCSIDs
other than 65535, consider changing such applications by replacing the mapping
scheme with CCSID support.
- Correctly define fields based on their usage. If fields contain application-dependent
values (for example, control characters or fields that are not used as real
character fields), define the fields as hexadecimal data or character fields
with CCSID 65535.
- Avoid using characters that are not in the invariant character set for
names and literals in programs.
Follow these guidelines when using CCSIDs:
- Use CCSIDs in multilingual applications to maintain character integrity
in database files, displays, and printed data.
- You can find a suggested CCSID for a language in Language identifiers
and associated default CCSIDs.
- If the QIGC system value is set on, set QCCSID as a mixed CCSID or 65535.
For more information about QIGC, see DBCS system indicator (QIGC) system value.
- If you use DBCS support, set the job CCSID to a mixed CCSID. If you do
not, set the job CCSID to a single-byte CCSID.
- Ensure that the QCHRID code page is compatible with the character set
and code page of the QCCSID value, unless the QCCSID value is 65535. If the
QCCSID value is changed to a value that is incompatible with the current QCHRID
value, the QCHRID value is changed to a compatible value by the system.
- If you use a user-defined data stream (UDDS), remove any X'3F' values
inserted by CCSID conversions. Otherwise, your data can cause the system to
blank out a screen. Some CCSID conversions use a X'3F' value for a substitution
character.
- If you are using any interactive jobs, such as Application Development
ToolSet/400, ensure that the code page of the job CCSID matches the code page
of the keyboard type. If these CCSID values do not match, or the job CCSID
is 65535, unpredictable results might occur. For more information, see National
language keyboard types and SBCS code pages.
- Be aware that the *JOBCCSID support is not used by any system-supplied
displays or panel groups, although CHRIDCTL support is used.
- Be aware of character data that has been defined or specified as control
information. For new database files, fields that contain control information
should be defined as hexadecimal data type or use CCSID 65535 instead of another
CCSID.
- Because of workstation hardware restrictions, you might not see all of
the characters on displays other than 3486, 3487, 3488, or Personal System/2
(PS/2®)
displays when CCSID conversion occurs. However, the character data is retained
in the system.
- Be aware that when a CCSID conversion is performed, substitution characters
might cause a loss of data. The situation occurs if enforced
subset match conversion is performed (see Conversion of character data).