For Oracle 9.2.0.3, first ensure you are using the 9.2 client (actually, its the 9.2.0.1 w/ the 9.2.0.3 patchset).
Now, follow these steps. Make sure you restart Impromptu after making the changes.
1. Open the Impromptu.ini file located at c

rogram files\cognos\cer3\bin. Under [Query Options], add this line: use automatic Oracle Decode=0
2. Open the codgmor.ini file located at c

rogram files\cognos\cer3\bin. Do a find and replace [Exceptions General ORACLEx.x], and replace all occurrences of Case_To_Decode=T to Case_To_Decode=F. These will be under the heading [Exceptions General ORACLEx.x], Add these lines for Oracle 9i below the lines for Oracle 8.1
[Exceptions General ORACLE9.0]
Case_To_Decode=F
[Exceptions General ORACLE9.1]
Case_To_Decode=F
[Exceptions General ORACLE9.2]
Case_To_Decode=F
3. Still in cogdmor.ini, under the section [Exceptions Valuesà] add these entries. Save and close file when completed.
[Exceptions Value Expressions ORACLE9.0]
Case=F
Case_Searched=F
Cast=F
[Exceptions Value Expressions ORACLE9.1]
Case=F
Case_Searched=F
Cast=F
[Exceptions Value Expressions ORACLE9.2]
Case=F
Case_Searched=F
Cast=F