Table not analyzed after partition has been split
Use the proper GRANULARITY option.

CREATE TABLE quarterly_regional_sales
      (deptno number, item_no varchar2(20),
       txn_date date, txn_amount number, state varchar2(2))
  PARTITION BY RANGE (txn_date)
    SUBPARTITION BY LIST (state)
      (PARTITION q1_1999 VALUES LESS THAN (TO_DATE('1-APR-1999','DD-MON-YYYY'))
         (SUBPARTITION q1_1999_northwest VALUES ('OR', 'WA'),
          SUBPARTITION q1_1999_southwest VALUES ('AZ', 'UT', 'NM'),
          SUBPARTITION q1_1999_northeast VALUES ('NY', 'VM', 'NJ'),
          SUBPARTITION q1_1999_southeast VALUES ('FL', 'GA'),
          SUBPARTITION q1_1999_northcentral VALUES ('SD', 'WI'),
          SUBPARTITION q1_1999_southcentral VALUES ('OK', 'TX')
         )
      );

SQL&gt; exec dbms_stats.gather_table_stats(user, 'QUARTERLY_REGIONAL_SALES');

PL/SQL procedure successfully completed.

SQL&gt;


SELECT TABLE_NAME, SUBPARTITION_NAME, NUM_ROWS, LAST_ANALYZED
FROM USER_TAB_SUBPARTITIONS 
WHERE TABLE_NAME = 'QUARTERLY_REGIONAL_SALES';

TABLE_NAME                     SUBPARTITION_NAME                NUM_ROWS LAST_ANALYZED
------------------------------ ------------------------------ ---------- -------------------
QUARTERLY_REGIONAL_SALES       Q1_1999_NORTHWEST                       0 2019-07-04 11:46:40
QUARTERLY_REGIONAL_SALES       Q1_1999_SOUTHWEST                       0 2019-07-04 11:46:40
QUARTERLY_REGIONAL_SALES       Q1_1999_NORTHEAST                       0 2019-07-04 11:46:40
QUARTERLY_REGIONAL_SALES       Q1_1999_SOUTHEAST                       0 2019-07-04 11:46:40
QUARTERLY_REGIONAL_SALES       Q1_1999_NORTHCENTRAL                    0 2019-07-04 11:46:40
QUARTERLY_REGIONAL_SALES       Q1_1999_SOUTHCENTRAL                    0 2019-07-04 11:46:40


Test1:

SQL&gt; exec DBMS_STATS.SET_PARAM ('GRANULARITY', 'GLOBAL');

PL/SQL procedure successfully completed.

SQL&gt; alter table QUARTERLY_REGIONAL_SALES split subpartition q1_1999_northwest into (subpartition q1_1999_northwest_1 values('OR'), subpartition q1_1999_northwest_2);

Table altered.

SQL&gt; exec dbms_stats.gather_table_stats(user, 'QUARTERLY_REGIONAL_SALES');

PL/SQL procedure successfully completed.

SELECT TABLE_NAME, SUBPARTITION_NAME, NUM_ROWS, LAST_ANALYZED
FROM USER_TAB_SUBPARTITIONS
  3  WHERE TABLE_NAME = 'QUARTERLY_REGIONAL_SALES';

TABLE_NAME                     SUBPARTITION_NAME                NUM_ROWS LAST_ANALYZED
------------------------------ ------------------------------ ---------- -------------------
QUARTERLY_REGIONAL_SALES       Q1_1999_NORTHWEST_1
QUARTERLY_REGIONAL_SALES       Q1_1999_NORTHWEST_2
QUARTERLY_REGIONAL_SALES       Q1_1999_SOUTHWEST                       0 2019-07-04 11:46:40
QUARTERLY_REGIONAL_SALES       Q1_1999_NORTHEAST                       0 2019-07-04 11:46:40
QUARTERLY_REGIONAL_SALES       Q1_1999_SOUTHEAST                       0 2019-07-04 11:46:40
QUARTERLY_REGIONAL_SALES       Q1_1999_NORTHCENTRAL                    0 2019-07-04 11:46:40
QUARTERLY_REGIONAL_SALES       Q1_1999_SOUTHCENTRAL                    0 2019-07-04 11:46:40

7 rows selected.


Test2:

SQL&gt; exec DBMS_STATS.SET_PARAM ('GRANULARITY', 'SUBPARTITION');

PL/SQL procedure successfully completed.

SQL&gt; alter table QUARTERLY_REGIONAL_SALES split subpartition Q1_1999_SOUTHEAST into (subpartition Q1_1999_SOUTHEAST_1 values ('FL'), subpartition Q1_1999_SOUTHEAST_2);

Table altered.

SQL&gt; exec dbms_stats.gather_table_stats(user, 'QUARTERLY_REGIONAL_SALES');

PL/SQL procedure successfully completed.

SELECT TABLE_NAME, SUBPARTITION_NAME, NUM_ROWS, LAST_ANALYZED
FROM USER_TAB_SUBPARTITIONS
  3  WHERE TABLE_NAME = 'QUARTERLY_REGIONAL_SALES';

TABLE_NAME                     SUBPARTITION_NAME                NUM_ROWS LAST_ANALYZED
------------------------------ ------------------------------ ---------- -------------------
QUARTERLY_REGIONAL_SALES       Q1_1999_NORTHWEST_1                     0 2019-07-04 11:52:31
QUARTERLY_REGIONAL_SALES       Q1_1999_NORTHWEST_2                     0 2019-07-04 11:52:31
QUARTERLY_REGIONAL_SALES       Q1_1999_SOUTHEAST_1                     0 2019-07-04 11:52:31
QUARTERLY_REGIONAL_SALES       Q1_1999_SOUTHEAST_2                     0 2019-07-04 11:52:31
QUARTERLY_REGIONAL_SALES       Q1_1999_SOUTHWEST                       0 2019-07-04 11:52:31
QUARTERLY_REGIONAL_SALES       Q1_1999_NORTHEAST                       0 2019-07-04 11:52:31
QUARTERLY_REGIONAL_SALES       Q1_1999_NORTHCENTRAL                    0 2019-07-04 11:52:31
QUARTERLY_REGIONAL_SALES       Q1_1999_SOUTHCENTRAL                    0 2019-07-04 11:52:31

8 rows selected.

SQL&gt;