Parallel execution is extremely slow for one SQL
Hi all,
The DB version is 11.1. Rac 4 nodes.
I have a query that is executed in parallel by default because some tables have parallel attribute.
The query ran too slow to be acceptable.
But if I disabled parallel query, it ended within one hour.
The tables being joined have 18M, 17M and 66M rows or so.
I think parallel query should be helpful here, but it didn't.
Could somebody give some advice on this case?
I don't know whether this has something to do with RAC configuration? Could it be because the parallel processes were distributed across different nodes and the inner processes communicatiion has some problems?
I know 11.2 has one parameter parallel_foce_local to foce parallel processes to run in local instance.
Does 11.1 have the similar parameter or undocumented parameter?
Thank you very much.
Leon