我们知道Oracle有DataGuard实时备份数据，可以做主备切换，而MySQL也有自己的一套备库方案，称之为主从复制。

搭建MySQL从库是为了实时同步主库数据，同时也可以分担主库的读压力，对数据库端做成读写分离结构。

搭建MySQL主从库注意点：

1.主库和从库的 server-id 一定不能相同。

2.在主库创建replication slave账户。

grant replication slave on *.* to 'repl'@'192.168.0.232' identified 'oracle';

3.查看主库master状态

mysql> show master status /G

*************************** 1. row ***************************

File: mysql-bin.000005

Position: 251651

Binlog_Do_DB:

Binlog_Ignore_DB:

1 row in set (0.00 sec)

4.配置从库

change master to

-> master_host='192.168.0.232',

-> master_user='repl',

-> master_password='oracle',

-> master_log_file='mysql-bin.000005',

-> master_log_pos=251651;

5. 启动从库

slave start

show slave status/G

*************************** 1. row ***************************

Slave_IO_State: Waiting for master to send event

Master_Host: ***********

Master_User: repl

Master_Port: 3306

Connect_Retry: 60

Master_Log_File: mysql-bin.000005

Read_Master_Log_Pos: 463725968

Relay_Log_File: mysql-relay-bin.000006

Relay_Log_Pos: 463726114

Relay_Master_Log_File: mysql-bin.000005

Slave_IO_Running: Yes

Slave_SQL_Running: Yes

Replicate_Do_DB: ******************

Replicate_Ignore_DB:

Replicate_Do_Table:

Replicate_Ignore_Table:

Replicate_Wild_Do_Table:

Replicate_Wild_Ignore_Table:

Last_Errno: 0

Last_Error:

Skip_Counter: 0

Exec_Master_Log_Pos: 463725968

Relay_Log_Space: 873569451

Until_Condition: None

Until_Log_File:

Until_Log_Pos: 0

Master_SSL_Allowed: No

Master_SSL_CA_File:

Master_SSL_CA_Path:

Master_SSL_Cert:

Master_SSL_Cipher:

Master_SSL_Key:

Seconds_Behind_Master: 0

Master_SSL_Verify_Server_Cert: No

Last_IO_Errno: 0

Last_IO_Error:

Last_SQL_Errno: 0

Last_SQL_Error:

Replicate_Ignore_Server_Ids:

Master_Server_Id: 100

注意：

如果从库Slave_IO_Running: No/ Slave_SQL_Running: No

关闭slave

设置set GLOBALSQL_SLAVE_SKIP_COUNTER=1;

在开启slave

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