Use ASCII data movement mode when all sources and targets are 7-bit ASCII or EBCDIC character sets. In ASCII mode, the PowerCenter Integration Service recognizes 7-bit ASCII and EBCDIC characters and stores each character in a single byte. When the PowerCenter Integration Service runs in ASCII mode, it does not validate session code pages. It reads all character data as ASCII characters and does not perform code page conversions. It also treats all numerics as U.S. Standard and all dates as binary data.
You can also use ASCII data movement mode when sources and targets are 8-bit ASCII.