mysql dba系统学习（7）二进制日志之三

二进制日志的相关系统变量

1，binlog_cache_size和max_binlog_cache_size

表示的为每一个session的事物分配的缓存

通常的当插入或者修改数据的时候，不会马上写磁盘，通常会缓存起来，缓存的大小有binlog_cache_size 来控制

mysql> show variables like"%binlog_cache%";

+-----------------------+----------------------+

| Variable_name| Value|

+-----------------------+----------------------+

| binlog_cache_size| 32768|

| max_binlog_cache_size |18446744073709547520 |

+-----------------------+----------------------+

2,binlog_cache_use

表示的是当前事物的数量

当前没有事物

mysql> showstatus like "%binlog_cache_use%";

+------------------+-------+

| Variable_name| Value |

+------------------+-------+

| Binlog_cache_use | 0|

+------------------+-------+

建立事物

mysql>show table status like 'tt'\G;

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

Name: tt

Engine: MyISAM（这种引擎不支持事物）

Version: 10

Row_format: Fixed

Rows: 1

Avg_row_length: 8

Data_length: 8

Max_data_length: 2251799813685247

Index_length: 1024

Data_free: 0

Auto_increment: NULL

Create_time: 2013-09-03 11:42:18

Update_time: 2013-09-03 15:24:13

Check_time: NULL

Collation: utf8_general_ci

Checksum: NULL

Create_options:

Comment:

1 row in set (0.00 sec)

mysql>drop table tt;

Query OK, 0 rows affected (0.01 sec)

mysql> create table tt(id int)engine=innodb; 设置成innodb的引擎

Query OK, 0 rows affected, 2 warnings (0.02sec)

mysql> insert into tt values(1);

Query OK, 1 row affected (0.00 sec)

mysql> show variables like"autocommit";

+---------------+-------+

| Variable_name | Value |

+---------------+-------+

| autocommit| ON|

+---------------+-------+

1 row in set (0.00 sec)

mysql> setautocommit=0;关闭自动提交事物

Query OK, 0 rows affected (0.00 sec)

mysql> show variables like"autocommit";

+---------------+-------+

| Variable_name | Value |

+---------------+-------+

| autocommit| OFF|

+---------------+-------+

1 row in set (0.01 sec)

mysql> insert into tt values(2);

Query OK, 1 row affected (0.01 sec)

mysql> commit;

Query OK, 0 rows affected (0.00 sec)

mysql>showstatus like"%binlog_cache_use%";

+------------------+-------+

| Variable_name| Value |

+------------------+-------+

| Binlog_cache_use | 2|

+------------------+-------+

1 row in set (0.00 sec)

3，max_binlog_size

表示的是二进制日志文件的大小

4，sync_binlog

当前的参数是0，说明由系统来控制何时同步

mysql> show variables like"%sync_binlog%";

+---------------+-------+

| Variable_name | Value |

+---------------+-------+

| sync_binlog| 0|

+---------------+-------+

1 row in set (0.00 sec)

若是这个参数是1，那么每次提交一个事物都会与磁盘同步一次数据

若是这个参数是2，那么每次提交二个事物都会与磁盘同步一次数据