select  a,
        b,
        c
  from  uid_tbl
  model
    dimension by(row_number() over(order by a) rn)
    measures(a,b,1 c,b s)
    rules(
          s[rn > 1] order by rn = case
                                    when nvl(s[cv() - 1],b[cv() - 1]) + b[cv()] >= 10 then null
                                    else nvl(s[cv() - 1],b[cv() - 1]) + b[cv()]
                                  end,
          c[rn > 1] order by rn = case
                                    when s[cv()] is null then c[cv() - 1] + 1
                                    else c[cv() - 1]
                                  end
         )
/

A                   B          C
---------- ---------- ----------
p1                  4          1
p2                  5          1
p3                  5          2
p4                  5          3
p5                  3          3
p6                  5          4

6 rows selected.

SQL> 

 DECLARE
  a NUMBER:=0;
  p NUMBER:1;
BEGIN
  FOR i IN
  (SELECT   UID,
           SUM(b)cnt from uid_tbl group by uid)
  

LOOP a:=a+i.cnt;
  
  IF a<10 THEN
    UPDATE uid_tbl
    SET    c=p
    WHERE  UID=i.UID;
  
  ELSIF a>=10 THEN
    p:=p+1;
    UPDATE uid_tbl
    SET    c=p
    WHERE  UID=i.UID;
    
    a:=i.cnt;
  END IF;
END LOOP;
END;