Maybe you could try add one line to the AOLserver wrapper script to set your environment variable. Open /usr/local/aolserver/bin/nsd-oracle and add this line
export NLS_LANG=.UTF8
Check if your aolserver config file in config.tcl has setting the defaults in the ns_section ns/parameters section (it is default for OACS 5.1)
ns_param DefaultCharset utf-8
Look at this thread https://openacs.org/forums/message-view?message_id=198856 too. Maybe could help you on utf-8 issues although it was about aolserver3.
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