title: DBMS output not printing
body: <p>Hi I want to write a ISBN validation in PLSql. But dbms_output.put_line doesnt output anything. I dont have any errors but dbms_output is yellow marked with the warning:</p>
  
  <blockquote>
    <p>Unable to resolve symbol 'dbms_output'</p>
    
    <p>Inspection info: This inspection performs unresolved SQL references check.</p>
  </blockquote>
  
  <p>. Im working in DataGrip and yes I have enabled SYS.dbms_output. </p>
  
  <pre><code>DECLARE
    v_isbn VARCHAR(13) := 9783161484100;
  BEGIN
    isbn_validation(v_isbn);
  end;
  
  CREATE OR REPLACE PROCEDURE isbn_validation
  (
      p_isbn VARCHAR
  )
  IS
    v_isbn VARCHAR(13);
    v_checksum INTEGER := 0;
  BEGIN
      if LENGTH(p_isbn) = 10 THEN
          v_isbn := CONCAT('978',p_isbn);
          v_checksum := isbn13_checksum(v_isbn);
          if(v_checksum = -1)THEN dbms_output.put_line(v_isbn || ' is a invalid isbn');
          else
            v_isbn:=CONCAT(v_isbn,CAST(v_checksum AS CHAR));
            isbn_validation(v_isbn);
            dbms_output.put_line(v_isbn || ' is a valid isbn');
          end if;
      elsif LENGTH(v_isbn) = 13 THEN
        v_checksum := isbn13_checksum(v_isbn);
          if(v_checksum = -1)THEN dbms_output.put_line(v_isbn || ' is a invalid isbn');
          else
            v_isbn:=CONCAT(v_isbn,CAST(v_checksum AS CHAR));
            isbn_validation(v_isbn);
            dbms_output.put_line(v_isbn || ' is a valid isbn');
          end if;
      end if;
  end;
  
  
  
  CREATE OR REPLACE FUNCTION isbn13_checksum
  (
      v_isbn VARCHAR
  )
  RETURN INTEGER
  IS
    v_checksum INTEGER := 0;
    v_remainder INTEGER := 0;
  BEGIN
      FOR i IN 1..12 LOOP
          if MOD(i,2) = 1 THEN
            if SUBSTR(v_isbn,i) = 'X' THEN
              v_checksum := v_checksum + 10;
            else v_checksum := v_checksum + CAST(SUBSTR(v_isbn,i) AS INTEGER);
            end if;
          else
            if SUBSTR(v_isbn,i) = 'X' THEN
              v_checksum := v_checksum + (10 * 3);
            else v_checksum := v_checksum + (CAST(SUBSTR(v_isbn,i) AS INTEGER) * 3);
            end if;
          end if;
      end loop;
      v_remainder := mod(v_checksum, 10);
      if v_remainder = 0 THEN RETURN -1;
      elsif(10-v_remainder)=10 THEN RETURN 0;
      else RETURN (10 - v_remainder);
      end if;
  end;
  </code></pre>