You can use the alter table command to:
Change an unpartitioned table to a multipartitioned table
Add one or more partitions to a list- or range-partitioned tables
Repartition a table for a different partitioning type
Repartition a table for a different partitioning key or bound
Repartition a table for a different number of partitions
Repartition a table to assign partitions to different segments
See the Reference Manual: Commands.
The general procedure for repartitioning a table is:
If the partition key or type is to change during the repartition process, drop all indexes on the table.
Use alter table to repartition the table.
If the partition key or type changed during the repartition process, re-create the indexes on the table.