Expand SGA but performance slow down?

Hello,
2 days ago I changed the init.ora and startup again. In init.ora,I changed the:
db_block_buffers = 200 --> 6400 shared_pool_size = 3500000 --> 10000000 log_buffer = 8192 --> 245760
processes = 50 -->100

After startup database again,the SGA allocated successfully. Database Buffers = 400K --> 12800KBytes Fixed Size=35K --> 31K
Redo Buffers=8K --> 240K
Variable Size=6887K --> 12526K

When I do the same SQL for a large amount of rows(about 37,000) for select and insert statement,
Before changed SGA,the statement takes 5 seconds to complete. After changed SGA,it takes 17 seconds to complete. Why???
Isn't the SGA more large more better?
If you know why,please tell me.
Please Cc to : violin.hsiao_at_mail.pouchen.com.tw,Thank you :) Received on Wed Aug 19 1998 - 01:04:54 CDT