I am also, 100% agreement with following statement:
"Setting something to parallel is no silver bullet", every thing depends on CPU, number of instances, Memory, and more over it depends on free server resources at time of your execution.

Also, how you setting up your Parallelism: instances or object level.

On the parallel issue, I was talking to an Oracle guru about the Oracle Parallel processes, and he was advocating to have 4-10 (based on degree of PARALLEL) datafiles for each tablespace, so when any one write or query to that tablespace, it will write/access simultaneously 4-10 datafiles as parallel processes.

Now, I am looking for any oracle documentation to verify his statement. He could not guide me to any doc, and saying it is from his experience. Does any one in this forum have any clue about this?

Thanks in advance,

OraMan