> On the other hand, if you look closely
> you will note that I've put:


Yes, I see... But I think that in my case it's moot, because it's a
read-only standby database that I'm trying to get Explain Plan working
in; creating a temporary table in a standard schema would not do much
for me here, as that schema will still be read only.

The only way I could make it work would be to either create another
tablespace which I could write to, or create the plan_table in the
temporary tablespace - neither of which is allowed.

I do not believe there's a way to make it work. Your comment about
updating the seq$ table convinces me even more.

Thanks for the insights; not the news I wanted, but at least I've done
due diligence. ;-)