SQL & PL/SQL :: To Add A Partition Into A Ranged Partitioned Table

I want to add a partition into a ranged partioned table but I receive error:

ALTER TABLE t_log
ADD
PARTITION p897_fft
VALUES
LESS THAN (898);

ORA-14074: partition bound must collate higher than that of the last partition

i check the high value like this:

SELECT partition_name, high_value
FROM dba_tab_partitions
WHERE table_name = 'T_LOG'
AND table_owner = 'PLAT'
[code]........

now, what to do? i dont want to remove Partition P899_MCDW. How to Split?