Hi

here is my comprehensive test result..where I have not dropped any partition neither there is data loss

SQL> drop table test
2 /

Table dropped.

SQL> create table test (c1 number) partition by range (c1)
2 ( partition p10 values less than (10),
3 partition p20 values less than (20),
4 partition p30 values less than (30),
5 partition pmax values less than (maxvalue))
6 /

Table created.

SQL> insert into test
2 values(31)
3 /

1 row created.

SQL> insert into test
2 values(41)
3 /

1 row created.

SQL> alter table test split partition pmax at (40) into (partition p40, partition pmax);

Table altered.

SQL> select * from test
2 /

C1
----------
31
41

SQL> select * from test partition(pmax)
2 /

C1
----------
41

SQL>

regards
Hrishy

P.S:do i understand your question right ?