Schultz, Charles wrote:
We had significant problems with sga_target, enough that we finally turned it off. Apparently, in 10.2.0.1 there are some issues with the algorithm that allocates/deallocates memory which can cause degradation.
Our Support Analyst(s) referenced the following bugs: 4466399/4472338 (dup) (SR 5386579.993): SYSTEM WIDE HANG ON MMON WAITING FOR 'SGA ALLOCATION FORCING COMPONENT GROWTH': 4507532 (SR 5256243.992): SGA_TARGET DOESN'T WORK AS EXPECTED
Not sure if this is relevant for your situation, but wanted to offer it up just in case.
Sincerely, Michael Ray Topshot Systems LLC -- http://www.freelists.org/webpage/oracle-l