In general, loading shift-sensitive character data can be much slower than loading simple ASCII or EBCDIC data. The fastest way to load shift-sensitive character data is to use fixed-position fields without delimiters. To improve performance, remember the following points:
The field data must have an equal number of shift-out/shift-in bytes.
The field must start and end in single-byte mode.
It is acceptable for the first byte to be shift-out and the last byte to be shift-in.
The first and last characters cannot be multibyte.
If blanks are not preserved and multibyte-blank-checking is required, then a slower path is used. This can happen when the shift-in byte is the last byte of a field after single-byte blank stripping is performed.