Converting values from one data type to another may cause values to be truncated.
Truncation can occur when:
Translating string data from a DT_WSTR to a DT_STR with the same length if the original string contains double-byte characters.
Casting an integer from a DT_I4 to a DT_I2 significant digits can be lost.
Casting an unsigned integer to a signed integer significant digits can be lost.
Casting a real number from a DT_R8 to a DT_R4 insignificant digits can be lost
Casting an integer from a DT_I4 to a DT_R4 insignificant digits can be lost.
The expression evaluator identifies explicit casts that may cause truncation and issues a warning when the expression is parsed. For example, the expression evaluator warns you if a 30-character string is cast into a 20-character string.
However, truncation is not checked at run time. At runtime data is truncated without warning. Most data adapters and transformations support error outputs that can handle the disposition of error rows.
For more information about handling truncation of data, see Error Handling in Data