COL1    COL2    COL3    COL4    COL5
----    ----    ----    ----    ----
A        1       K       1       N
A        1       K       50      J
A        1       K       99      R
B        2       J        1      N
B        2       J        5      N
C        3       M        8      N
C        3       M        99     U
D        7       R        2      L

COL1    COL2    COL3    COL4    COL5
----    ----    ----    ----    ----
A        1       K       99      R  (eliminated two other records)
B        2       J        1      N
B        2       J        5      N
C        3       M        99     U  (eliminated one other record)
D        7       R        2      L

SQL> select * from test;

C       COL2 C       COL4 C
- ---------- - ---------- -
A          1 K          1 N
A          1 K         50 J
A          1 K         99 R
B          2 J          1 N
B          2 J          5 N
C          3 M          8 N
C          3 M         99 U
D          7 R          2 L

8 rows selected.

SQL> select * from test
  2  where col4 = 99
  3  union
  4  select * from test
  5  where (col1, col2, col3) not in (select col1, col2, col3
  6                                   from test
  7                                   where col4 = 99
  8                                  );

C       COL2 C       COL4 C
- ---------- - ---------- -
A          1 K         99 R
B          2 J          1 N
B          2 J          5 N
C          3 M         99 U
D          7 R          2 L

SQL>