Oracle taking whole memory

Hi , I am facing a memory issue in  Oracle database 11.2.0.1.0 on Linux platform. Oracle starts taking memory when even a count(*) query is executed & reaches upto 21G .This is observed even after disabling Automatic memory management.

Below are the parameters given...
memory_max_target             big integer 10G
memory_target                 big integer 10G

Below are our information.

After restart of server (OS)

top - 17:58:31 up 9 min,  3 users,  load average: 0.17, 0.27, 0.22
Tasks: 284 total,   1 running, 283 sleeping,   0 stopped,   0 zombie
Cpu(s):  0.1%us,  0.0%sy,  0.0%ni, 99.9%id,  0.0%wa,  0.0%hi, 0.0%si,  
0.0%st
Mem:     24152M total,      917M used,    23235M free,       10M buffers
Swap:    24575M total,        0M used,    24575M free,      317M cached