a SAVEPOINT control statement is not permitted within a SQL
  function definition

  Explanation:  Neither a SAVEPOINT, ROLLBACK TO SAVEPOINT nor SET
  TRANSACTION statement is permitted within an SQL function.
  These statements may only be used in a SQL stored procedure, or
  an anonymous compound statement (also known as a multi-statement
  procedure).

  User Action:  Define the SQL function without any SAVEPOINT
  control statements.