NLS_LANG is used to indicate to Oracle what character set your client's OS is using. Using this information, Oracle can perform, if necessary, a conversion from the client's character set to the database character set. Setting NLS_LANG to the character set of the database may be correct but is not always correct. Do not assume that NLS_LANG must always be the same as the database character set. Oracle recommends that you use the AL32UTF8 character set. This is based on information found in the Oracle document titled Doc ID: 158577.1 NLS_LANG Explained (How does Client-Server Character Conversion Work?). You cannot change the character set of your client by using a different NLS_LANG setting.