I'm trying out oracles parallel option on a cluster and surprisingly I am getting worse results with the parallel option. I was expecting some improvement with the parallel option but certainly not worse results. I am wondering why this is the case, and if there is anything wrong with the way I am using the parallel option on my cluster.
I am using a degree of 4 when the number of CPU's I have is 8. I have tried adding parallel to the cluster directly
ALTER CLUSTER cluster PARALLEL 4 as well as at the statement on both the index
/*+ PARALLEL_INDEX(clust_index, 4) */and tables
/*+ PARALLEL(4) */,
Here is my trace from the parallel: