The HEX function returns a character-string value  that  is  the
  hexadecimal  equivalent  of the specified parameter.  The return
  value is compatible with all other string types.

  Syntax:

     HEX( x [[, length[[, digits]]]] )

  The parameter 'x' is  the  expression  to  be  converted.   This
  parameter  must  have  a  size that is known at compile time; it
  cannot be VARYING OF CHAR, a conformant parameter, or  a  schema
  type.

  Two optional  integer  parameters  specify  the  length  of  the
  resulting string and the minimum number of significant digits to
  be returned.  If you specify a length that is too short to  hold
  the  converted  value,  the resulting string is truncated on the
  left.  If you do not specify values for the optional parameters,
  a  default  length and a default number of significant digits is
  used.

  By default, the number of  significant  digits  is  the  minimum
  number  of  characters  necessary to express all the bits of the
  converted parameter.  This default length is one character  more
  than  the default number of digits, which causes a leading blank
  to be included in the resulting string when both parameters  are
  omitted.