Question: varchar2 20 byte is how many characters?
Answer: For instance, a VARCHAR2(20 BYTE) column in an AL32UTF8 database could hold 20 characters from the ASCII range, 10 Latin letters with umlaut, 10 Cyryllic, 10 Hebrew, or 10 Arabic letters (2 bytes per character), or 6 Chinese, Japanese, Korean, or Devanagari (Indic) characters.