Mysql备份时报错：mysqldump: Got error: 1016: Can't open file: '**.fr..

mysqldump: Got error: 1016: Can't open file: './vos/e_syslog_20200405.frm' (errno: 24) when using LOCK TABLES

mysqldump：获取错误：1016：无法打开文件：‘/vos/e_syslog_20200405.frm’（错误：24）当使用LOCK标签时。

-->通过报错信息可以判断是Mysql打开了太多的文件，而打不开新的文件了。 

[root@vos~]# mysqldump -uroot -p123456 --lock-tables=false vos > test.sql

[root@vos]# mysql -uroot -p123456

mysql> show variables like 'open%';   //查看当前打开文件的限制数
+------------------+-------+
| Variable_name    | Value |
+------------------+-------+
| open_files_limit | 1024  | 
+------------------+-------+
1 row in set (0.00 sec)

[root@vos23 ~]# vim /etc/my.cnf    //打开my.cnf添加以下配置
[mysqld]
...
open_files_limit=65535   

[root@vos]# systemctl restart mysqld    //重启mysql服务   

mysql> show status like 'open%';    //查看打开的参数
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Open_files    | 640   |     //当前打开的文件数
| Open_streams  | 0     | 
| Open_tables   | 320   | 
| Opened_tables | 0     | 
+---------------+-------+

mysql> show open tables;     //查看打开了哪些表
+----------+------------------------------+--------+-------------+
| Database | Table                        | In_use | Name_locked |
+----------+------------------------------+--------+-------------+
| vos  | e_conference_record_20200206 |      0 |           0 | 
| vos  | e_cdr_20200101               |      0 |           0 | 
| vos  | e_cdr_20200125               |      0 |           0 | 
| vos  | e_payhistory                 |      0 |           0 | 
| vos  | e_cdr_20200326               |      0 |           0 | 
| vos  | e_cdr_20200402               |      0 |           0 | 
...

mysql> show variables like 'max_prepared%';
+-------------------------+-------+
| Variable_name           | Value |
+-------------------------+-------+
| max_prepared_stmt_count | 16382 | 
+-------------------------+-------+

mysql> flush tables;