same secondary index cols defined on join index also

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same secondary index cols defined on join index also

same secondary index cols defined on join index also

Greetings Experts,

Is this accepted form?

Table abc with columns col1, col2, col3,.....

with a composite secondary index on abc_s1(col2, col3)

There is a join index on the table abc with name as ji_abc (ofcourse with different PI)

Join index ji_abc with columns col1, col2, col3,.....

and a secondary index defined on the same set of columns as that of the base table as ji_abc_s1(col3, col2) with change in order.

I believe that the position of the columns defined in composite secondary index doesn't matter.  Does defining the same set of indexes on base table and on join index help in any way as there is more overhead during DML operations.  

Is this situation an ideal one when the base table is a bit skewed and we create a join index in such a way that there are no skewness, there by if the secondary index is a NUSI, it can be benefited.