What are global and local index?

Global Index : A single index covering all partitions.

Local Index : Separate indexes for each partition. A local index can be unique. However,
in order for a local index to be unique, the partitioning key of the table must be part of the index key columns.
Unique local indexes are useful for OLTP environments. You cannot explicitly add a partition to a local index.
Instead, new partitions are added to local indexes only when you add a partition to the underlying table.