[CentOS] CENTOS 5.5 segfault what it mean??

We have CENTOS 5.5 on DELL server and several ORACLE databases on version 10.2.0.4 and 11.1.0.7.  Recently I found following messages popup on /var/log/messages:


Jul 26 16:28:03 ORA6 kernel: oracle[29286]: segfault at fffffffffffffff0 rip 0000000007d54183 rsp 00007fffff6c3080 error 4
Jul 26 16:28:07 ORA6 kernel: oracle[29300]: segfault at fffffffffffffff0 rip 0000000007d54183 rsp 00007fff47838560 error 4
Jul 26 16:28:11 ORA6 kernel: oracle[29309]: segfault at fffffffffffffff0 rip 0000000007d54183 rsp 00007fffda1a3ee0 error 4
Jul 26 16:28:15 ORA6 kernel: oracle[29322]: segfault at fffffffffffffff0 rip 0000000007d54183 rsp 00007fff97087220 error 4
Jul 26 16:28:19 ORA6 kernel: oracle[29337]: segfault at fffffffffffffff0 rip 0000000007d54183 rsp 00007fffb3647280 error 4

I can not find and trace file or core dump file on O.S. and ORACLE databases.  I also check hardware log and NO memory or disks error.

Any ideal?