Where is the official Oracle i18n FAQ ?

http://technet.oracle.com/products/oracle8i/htdocs/faq_combined.htm

What env. variable affect my nantional language settings ?

NLS_LANG

How will I check my current NLS lang settings of my database ?

Issues this SQL command.

select * from v$nls_parameters ;

Can I use variable width multi-byte names for datafile, log file etc. ?

No. See Oracle's "Database Globalization Support Guide" for the restrictions on database character sets.

How can we retrieve,store the japanese data into the oracle databse ?

Here are the general steps to store the Japanese data
in Oracle.

1) Decide on the charset first. As you might know
there are three popular charset to store Japanese
data. Viz. JA16EUC, JA16SJIS and UTF8.

couple of factors decide which charset to go. One is
from where you are getting this data. E.g if you are
getting from User using a Java application, then you
might want to go for UTF8 (Since Unicode(UTF-16) to
UTF-8 conversion is faster). Also if you want to
handle other language other then Japanese UTF8 is
good.

If it is a Solaris based application where the data
will be in JA16EUC then you might want to go for that
one.

2) Once you decide on the charset use that in your
"create database" statement. Look at the document for
the keyword "character set" in the create database
statement.

3) Then set the NLS_LANG to JAPANESE_JAPAN. <charset>
Where <charset> is the charset you choose in step 2.

4) While accessing using JDBC etc, It automatically
converts the charset to the Java Unicode string. If
you run into any problem here, you can specifically
set the charset parameter in the connection
properties.

Hope this helps