早上查看数据库alert日志，发现如下ORA-报错：
kgxpvfynet: mtype: 61 process 6460 failed because of a resource problem in the OS. The OS has most likely run out of buffers (rval: 4)
Errors in file /u01/app/oracle/diag/rdbms/orcl/orcl2/trace/orcl2_ora_6460.trc (incident=176003):
ORA-00603: ORACLE server session terminated by fatal error
ORA-27504: IPC error creating OSD context
ORA-27300: OS system dependent operation:sendmsg failed with status: 105
ORA-27301: OS failure message: No buffer space available
ORA-27302: failure occurred at: sskgxpsnd2
经过搜索MOS ，给出的结论是： 这是由于网络缓冲区保留空间不足造成的。
vm.min_free_kbytes should be set in the order of 0.4% of total Physical Memory
解决方案：
1. 增大操作系统内核参数vm.min_free_kbytes 的值
由于本机物理内存128G，故此处增大到： vm.min_free_kbytes = 524288
sysctl -p 使参数生效
2. 还建议修改lo网卡MTU的值
#ifconfig lo mtu 16436
#vi /etc/sysconfig/network-scripts/ifcfg-lo