Index Unusable Option 
Set the indexes on the latest partitions to be "unusable", 
do as many concurrent inserts as we want, then rebuild the index. 
The only indexes this is an issue for is BITMAP indexes. 
Regular B-TREE indexes are fine.  

For example if we had hourly partitions like Oct 16 1am ie _10_16_01 we could
have the following partitions for CM_HOUR_FACTS for the 7 Bitmap indexes it has:

alter index TOTO_I     modify partition P_2007_10_16_01 unusable;

we then load the data for an hour.
Each session loading data has to set ( as well as any sessions selecting data )

    alter session set skip_unusable_indexes = true;

after the data is loaded then we rebuild those indexes

alter index TOTO_I     rebuild partition P_2007_10_16_01   ;

For a list of unusable index partitions see

select index_name,partition_name, status  from all_ind_partitions where
lower(index_name) like '%_CM_HOUR_FACTS%' and status='UNUSABLE'
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