install/codepage/MNLS_CONVERSION is a SAP Parameter attribute which is used to control Don't translate Japanese characters to upper case information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
Even if you are not in asiatic double-byte characater mode, there can be
special systems that process Japanese characters. This switch activates
an additional function that prevents the DBC character of the level 1
Kanji range in such cases from being destroyed by a TRANSLATE ..TO UPPER
CASE function.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.