AVM from your vmstat output

660500*4096=2705408000
2705408000/1024/1024=2580MB

You only have 2GB, this means that you have more AVM than memory and
yes you will be paging out to paging space. This is ok, but
performance will suffer as disk latency at best is 10,000 times slower
than memory latency.

You need to buy some more memory for you current work load, or reduce
the size of your SGA.

HTH
Mark Taylor