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 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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