Oracle Database Discussions

Hi

i have an oracle database server which contains 4 instances, sometimes this last day the server accounter a load problem and CPU is used 10O%. the process consuming that much resources are Oracle process but i don't know which of the instane. could you advise please how to find the instanecs eating to much resource.
we are runing on Linux SUSE 32 bits with Oracle 10g r2.

here is the output of the top command:

Tasks: 334 total, 20 running, 314 sleeping, 0 stopped, 0 zombie
Cpu(s): 22.3%us, 4.5%sy, 0.0%ni, 68.0%id, 3.6%wa, 0.1%hi, 1.5%si, 0.0%st
Mem: 20791076k total, 10802972k used, 9988104k free, 125996k buffers
Swap: 4194288k total, 370532k used, 3823756k free, 8985672k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
19235 oracle 16 0 1641m 296m 285m R 25 1.5 6:35.09 oracle
18456 oracle 16 0 1645m 270m 257m R 18 1.3 11:04.74 oracle
16878 oracle 16 0 1645m 342m 328m R 13 1.7 21:04.50 oracle
19933 oracle 16 0 1637m 235m 228m R 13 1.2 3:37.11 oracle
16293 oracle 15 0 1645m 361m 347m R 12 1.8 25:34.91 oracle
16738 oracle 16 0 1645m 321m 307m R 10 1.6 20:55.88 oracle
17930 oracle 16 0 1645m 291m 278m R 10 1.4 14:05.26 oracle
22558 oracle 16 0 1635m 192m 187m R 10 0.9 1:06.10 oracle
15530 oracle 16 0 1677m 552m 505m R 7 2.7 41:42.85 oracle
16940 oracle 16 0 1645m 365m 351m R 7 1.8 20:37.96 oracle
22046 oracle 16 0 1219m 336m 330m R 5 1.7 1:49.29 oracle
6712 oracle 15 0 1488m 802m 799m S 3 4.0 1:03.66 oracle
18424 oracle 16 0 1216m 157m 154m R 3 0.8 0:13.40 oracle
6710 oracle 15 0 1486m 883m 882m S 1 4.4 0:15.12 oracle

We suspect one of our instance, would you please tell me how to check the sql code which is eating to much resource causing this hang.

Thank you

Lucienot.