Use
You can use SAP_CMMODCONVTAB to modify a contiguous area in the current conversion table. This allows you to change the conversion of individual characters. You can only change either the ASCII ® EBCDIC table or the EBCDIC ® ASCII table.

CM_RETCODE return_code;
..
SAP_CMMODCONVTAB(EBCDIC_TABLE, 193, "4243", &return_code);
..
The above modification results in the following (not very useful) conversion:
EBCDIC character |
® |
ASCII character |
A |
® |
B |
B |
® |
C |
All subsequent CMCNVI and CMCNVO calls work with the modified conversion table.