SQL*Plus will spool out a number of rows corresponding to the SQL*Plus PAGESIZE setting before it will spool the column headers again. The default PAGESIZE is 14.
SQL>
SQL> set pagesize 4
SQL>
SQL> select rownum, object_name
2 from all_objects
3 where rownum < 20
4 /
ROWNUM OBJECT_NAME
---------- ------------------------------
1 ICOL$
ROWNUM OBJECT_NAME
---------- ------------------------------
2 I_USER1
ROWNUM OBJECT_NAME
---------- ------------------------------
3 CON$
ROWNUM OBJECT_NAME
---------- ------------------------------
4 UNDO$
ROWNUM OBJECT_NAME
---------- ------------------------------
5 C_COBJ#
ROWNUM OBJECT_NAME
---------- ------------------------------
6 I_OBJ#
ROWNUM OBJECT_NAME
---------- ------------------------------
7 PROXY_ROLE_DATA$
ROWNUM OBJECT_NAME
---------- ------------------------------
8 I_IND1
ROWNUM OBJECT_NAME
---------- ------------------------------
9 I_CDEF2
ROWNUM OBJECT_NAME
---------- ------------------------------
10 I_PROXY_ROLE_DATA$_1
ROWNUM OBJECT_NAME
---------- ------------------------------
11 FILE$
ROWNUM OBJECT_NAME
---------- ------------------------------
12 UET$
ROWNUM OBJECT_NAME
---------- ------------------------------
13 I_FILE#_BLOCK#
ROWNUM OBJECT_NAME
---------- ------------------------------
14 I_FILE1
ROWNUM OBJECT_NAME
---------- ------------------------------
15 I_CON1
ROWNUM OBJECT_NAME
---------- ------------------------------
16 I_OBJ3
ROWNUM OBJECT_NAME
---------- ------------------------------
17 I_TS#
ROWNUM OBJECT_NAME
---------- ------------------------------
18 I_CDEF4
ROWNUM OBJECT_NAME
---------- ------------------------------
19 IND$
19 rows selected.
SQL>
SQL> set pagesize 300
SQL>
SQL> select rownum, object_name
2 from all_objects
3 where rownum < 20
4 /
ROWNUM OBJECT_NAME
---------- ------------------------------
1 ICOL$
2 I_USER1
3 CON$
4 UNDO$
5 C_COBJ#
6 I_OBJ#
7 PROXY_ROLE_DATA$
8 I_IND1
9 I_CDEF2
10 I_PROXY_ROLE_DATA$_1
11 FILE$
12 UET$
13 I_FILE#_BLOCK#
14 I_FILE1
15 I_CON1
16 I_OBJ3
17 I_TS#
18 I_CDEF4
19 IND$
19 rows selected.