Oracle Exadata, db_file_multiblock_read_count and sort_multiblock_read_count

Hi,
I have an Oracle RDBMS 11gR2 EE that uses ASM and Exadata.
We have sone processes that read huge amount of data, "shuffle it" and insert it to tales. Totally, about 20% of the data is processed.
The total size of the database is about 12 TB.
Most of these processes perform a full table scans, using also the Exadata smart scans.
Some ad-hoc indexes are created and can be used as well. All this through hints (because the data is shuffeled, statistics are not accurate anymore).
As we consequence, we have quite noticeable and very long running processes (from hours to few days).
It consumes also a significant amount of temporary tablespace.
We would like to investigate if it is possible to "speed up" that whole process.
I have found that the following parameter could be used to minimize disk I/O:
db_file_multiblock_read_count
But I have read pros et cons about it... so I am confused about using it properly.
Additionally, there is also this parameters:
sort_multiblock_read_count
Do these parameters also apply when having these smart scans?
If these parameters can improve throughput, how can I find out the size they should be?
What are the advantages and disadvantages of using them?
Thanks by advance for sharing your experence.
Kind Regards.

Hi Franck,
Not all tables are compresses, and the index are used to access intermediate look-up tables.
The content of the tables is practically "flushed out" as part of an anonimization process. So, at that stage statistics are not accurate anymore, and thus a hint is the only way to "force" a full scan (as the whole content of the tables need to be accessed). Is this is the right plan, that is another question that I cannot directly answer as the "logic" in the statements is not always the same. The full table scans with smart scans ranges from 60 to 90% which I think is quite good (although mu knowledge of Exadata is rather limited).
I agree with you to not change the mentioned parameters.
Kind Regards.

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