While running autoconfig in oracle apps on database side, you might encounter this error. Also you can see this when you do sqlplus from command prompt.
Either your NLS_LANG parameter is not set correctly or NLS_ORA10 parameter is not set correctly.
check $ORA_NLS10 path. This should point to ORACLE_HOME/nls/data/9idata
if this is not set correct, then you need to set the same manually using export command. Also if this is an oracle application database ( either 11i or R12), then make sure to change the variable s_db_oranls in CONTEXT_FILE and then run autoconfig.
If ORACLE_HOME/nls/data/9idata path is not present then you can create the same using $ORACLE_HOME/nls/data/old/cr9idata.pl script. Run this script and it will create the desired directories and after that set ORA_NLS10 parameter.
If this doesn’t resolve the issue then you need to check NLS_LANG parameter setting. This should be (Language)_(Territory).(character set). Example American_America.UTF8.
Hope this helps !!