意思是mycat.pid文件过期了，只需要删除该文件，然后重启即可。
[root@db01 ~]# mycat start
Starting Mycat-server...
Removed stale pid file: /application/mycat/logs/mycat.pid
[root@db01 ~]# rm -rf /application/mycat/logs/mycat.pid
[root@db01 ~]# mycat start
Starting Mycat-server...
[root@db01 ~]# mysql -uroot -p123 -h 127.0.0.1 -P8066
mysql: [Warning] Using a password on the command line interface can be insecure.
ERROR 1045 (HY000): Access denied for user 'root', because password is error
[root@db01 ~]# mysql -uroot -p123456 -h 127.0.0.1 -P8066
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.6.29-mycat-1.6.5-release-20180122220033 MyCat Server (OpenCloundDB)
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Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql>
