I've left Solaris behind at version 9, but from my very limited experience (~15 years) the total CPU a single process can consume is equal to 100/number of CPUs you have. For example, if you have a four CPU box, any one CPU will never get past 25%. You have a 32 CPU machine, so any one process will never get past 3.2%.

Now, that's not to say you don't have some throttling software on your box, but I doubt it.

Part of your problem is this:
Code:
Execute 1 260.09 268.77 0 0 0 1
Execute 2 1592.53 1555.19 0 0 0 1
In the second case, you're executing the PL/SQL block twice, or double the work of the first. In theory, that puts your comparison of 4.5 mins to about 12 mins.

The strength of your Solaris box isn't it's raw computing power. It's the near linear scalability of the CPUs and the rock-solid reliability of the OS/Hardware combination. But you're seeing why so many people, myself included, have moved away from Sun and onto commodity servers.