db file sequetial read while performing insert

Hello,

We have top insert statement with high IO in OEM if we go at SQL level it shows db file sequential read wait event

any script to check if it is correct index and it is not skew one. How to implement reverse index?

It is doing sequetial read as clear in below output as P3=1

My db version is 11.2.0.4

db_multi_block_read set to default and when I do show parameter then value shows 128.

Let me know some script and area to check and based on that I can fix the issue.

Note: I ran sqltuning and it suggested to create two indexes and hence I created but I do not see any improvement.