oracle linux 常用
修改链接数
show parameter processes

alter system set processes=2000 scope=spfile;

查看连接个数

select count(*) from v$session where status='ACTIVE';

Too many open files in system
echo "9234560">/proc/sys/fs/file-max

linux Too many open files in system

查看各个进程打开的文件数据量
# lsof -n |awk '{print $2 " " $3}'|sort|uniq -c |sort -nr|more

sshkey
ssh-keygen -t dsa -f /etc/ssh/ssh_host_dsa_key
ssh-keygen -t rsa -f /etc/ssh/ssh_host_rsa_key

释放内存
echo 1 > /proc/sys/vm/drop_caches
echo 2 > /proc/sys/vm/drop_caches
echo 3 > /proc/sys/vm