Oracle 为庆祝 MySQL 30 周年，截止到 2025.07.31 之前。所有人均可以免费考取原价245美元的MySQL OCP 认证。

从今天开始，将英文题库免费公布出来，并进行解析，帮助大家在一个月之内轻松通过OCP认证。

本期公布试题16~25

试题16:

choose two.Examine the modified output:mysql> 
SHOW SLAVE STATUS\G
******************1. row******************** 
Slave_IO_Running:Yes
Slave_SQL_Running:Yes 
Seconds_Behind_Master:1612 
Seconds_Behind_Master value is steadily growing. What are two possible causes? 


B)This value shows only I/O latency and is not indicative of the size of the transaction queue. [错误] 

A)The master is producing a large volume of events in parallel but the slave is processing them serially. [正确] 

C)One or more large tables do not have primary keys. [错误] 

E)The parallel slave threads are experiencing lock contention. [错误] 

D)The master is most probably too busy to transmit data and the slave needs to wait for more data. [正确]

解析

本题考查主从问题，从题目中可以看到IO线程和SQL线程均正常，延迟有1612秒，题目问造成主从延迟持续稳定增长的两种可能的原因是什么？

B)This value shows only I/O latency and is not indicative of the size of the transaction queue.  [错误] 
该值仅显示 I/O 延迟，并不表示事务队列的大小。
该指标反映的是SQL线程与I/O线程的整体延迟，不仅是I/O延迟

A)The master is producing a large volume of events in parallel but the slave is processing them serially. [正确] 
主服务器正在并行生成大量事件，但从服务器正在串行处理它们。这是造成延迟的一个原因之一，正确。


C)One or more large tables do not have primary keys. [错误]
一个或多个大型表没有主键。无主键表会导致复制效率降低，但不会直接表现为延迟持续增长

E)The parallel slave threads are experiencing lock contention. [错误] 
并行从属线程遇到锁争用。并行复制线程锁竞争会导致延迟波动，而非稳定增长


D)The master is most probably too busy to transmit data and the slave needs to wait for more data. [正确]
主服务器很可能太忙而无法传输数据，而从服务器需要等待更多数据。

选项正确原因：
    主库网络带宽不足或负载过高时，Binlog传输速度会变慢
    从库I/O线程无法及时获取新事件，导致SQL线程空闲等待
    表现为Slave_IO_Running: Yes但延迟持续增加

对于选项A的情况，可考虑启用从库的并行复制功能（slave_parallel_workers）
对于选项D的情况，需检查主库网络状况和binlog_dump线程状态

试题17:

Choose two.Which two are true about binary logs used in asynchronous replication? 
A)The master connects to the slave and initiates log transfer. [错误] 
B)They contain events that describe all queries run on the master. [错误] 
D)They are pulled from the master to the slave. [正确] 
C)They contain events that describe database changes on the master. [正确] 
E)They contain events that describe only administrative commands run on the master. [错误] 

解析

关于异步复制中使用的二进制日志，哪两个是正确的？

A)The master connects to the slave and initiates log transfer. [错误] 
主服务器连接到从服务器并启动日志传输。
错误 - 主库不会主动连接从库，复制方向完全由从库发起

B)They contain events that describe all queries run on the master. [错误] 
它们包含描述在 master 上运行的所有查询的事件。
错误 - 二进制日志不记录所有查询（如SELECT/show等只读操作不会被记录）

D)They are pulled from the master to the slave. [正确] 
它们从 master 拉到 slave。

C)They contain events that describe database changes on the master. [正确] 
它们包含描述主服务器上的数据库更改的事件。
二进制日志记录的是"数据变更事件"（如DML语句、表结构变更等），而非原始SQL语句
以"事件"形式记录能保证跨版本兼容性和确定性执行
注意：binlog_format=ROW时记录行变更，STATEMENT时记录原始SQL（但仍是事件形式封装）

E)They contain events that describe only administrative commands run on the master. [错误] 它们包含仅描述在主服务器上运行的管理命令的事件
不仅记录管理命令，所有数据变更（INSERT/UPDATE等）都会记录

试题18:

You have appropriate privileges and are about to shut down a running MySQL server process on Oracle Linux 7.Which three are valid methods that will shut down the MySQL server? 

E)mysqld_safe --shutdown [错误] 
A)mysqld_safe -S /tmp/mysql.sock SHUTDOWN [错误] 
B)kill mysqld_safe [错误] 
F)systemctl stop mysqld  [正确] 
G)mysql> SHUTDOWN; [正确] 
D)mysql -S /tmp/mysql.sock --shutdown [错误] 
C)mysqladmin shutdown  [正确]

解析

您具有适当的权限，并且即将关闭 Oracle Linux 7 上正在运行的 MySQL 服务器进程。哪三种方法是将关闭 MySQL 服务器的有效方法？

E)mysqld_safe --shutdown [错误] 
mysqld_safe不支持--shutdown参数（这是早期版本的误传）

A)mysqld_safe -S /tmp/mysql.sock SHUTDOWN [错误] 
mysqld_safe没有-S参数，也不接受SHUTDOWN指令

B)kill mysqld_safe [错误] 
直接kill mysqld_safe进程可能导致非正常关闭

F)systemctl stop mysqld  [正确] 

G)mysql> SHUTDOWN; [正确] 

D)mysql -S /tmp/mysql.sock --shutdown [错误] 
mysql客户端没有--shutdown参数

C)mysqladmin shutdown  [正确]
MySQL官方提供的管理工具

试题19:

Choose two.Examine this MySQL Shell command:dba.rebootClusterFromCompleteOutage () Which two statements are true? 

E)It reconfigures InnoDB Cluster if the cluster was stopped. [错误] 
D)It performs InnoDB Cluster instances rolling restart. [正确] 
A)It stops and restarts all InnoDB Cluster instances and initializes the metadata. [错误] 
F)It picks the minimum number of instances necessary to rebuild the quorum and reconfigures 
InnoDB Cluster. [错误] 
C)It is not mandatory that all instances are running and reachable before running the command. [正确] 
B)It only stops and restarts all InnoDB Cluster instances. [错误] 
G)It only starts all InnoDB Cluster instances. [错误] 

解析

本题考查mysql shell的使用，dba.rebootClusterFromCompleteOutage() 是 MySQL Shell 中用于 从完全宕机状态恢复 InnoDB Cluster 的关键命令，主要解决集群因意外故障导致所有节点不可用后的恢复问题。

正确选项：
D) 执行InnoDB Cluster实例的滚动重启
C) 运行该命令前不要求所有实例都必须在线且可访问


E)It reconfigures InnoDB Cluster if the cluster was stopped. [错误] 
如果集群已停止，它会重新配置 InnoDB Cluster
错误：描述不准确，该命令专为完全宕机场景设计

D)It performs InnoDB Cluster instances rolling restart. [正确] 
它执行 InnoDB Cluster 实例滚动重启

A)It stops and restarts all InnoDB Cluster instances and initializes the metadata. [错误] 
它会停止并重新启动所有 InnoDB Cluster 实例并初始化元数据。
错误，不会显式停止实例，而是针对已停止的集群进行恢复

F)It picks the minimum number of instances necessary to rebuild the quorum and reconfigures InnoDB Cluster. [错误] 
它选择重建 quorum 所需的最小实例数并重新配置 InnoDB Cluster。
错误：不是选择"最少实例"，而是基于现存实例重建仲裁

C)It is not mandatory that all instances are running and reachable before running the command. [正确] 
在运行命令之前，并非所有实例都正在运行且可访问。

B)It only stops and restarts all InnoDB Cluster instances. [错误] 
它仅停止并重新启动所有 InnoDB Cluster 实例。
错误：并非简单重启，重点是重建集群元数据和拓扑

G)It only starts all InnoDB Cluster instances. [错误] 
它仅启动所有 InnoDB Cluster 实例
错误：包含元数据重建等复杂操作，非单纯启动实例

试题20:

Choose two.Examine this command and output:（见下图）Which two options will improve the security of the MySQL instance?

D)Change the parent directory owner and group to mysql. [错误] 
A)Remove the world read/execute privilege from the accounting directory. [正确] 
F)Remove group read/write privileges from the private_key.pem file. [正确] 
E)Remove world read privileges from the server-cert.pem certificate file. [错误] 
B)Remove world read privileges from the public_key.pem file. [错误] 
C)Change the group ownership of the mysql directory to the mysql user group. [错误] 

解析

哪两个选项将提高 MySQL 实例的安全性？

A) 移除accounting目录的全局读/执行权限
F) 移除private_key.pem文件的组读写权限

D)Change the parent directory owner and group to mysql. [错误] 
修改父目录属主为mysql
父目录已属于mysql:mysql，无需修改（且可能影响其他服务）。

A)Remove the world read/execute privilege from the accounting directory. [正确] 
目录权限为 drwxrwxr-x 表示其他用户（world）有读和执行权限，可能导致未授权用户遍历目录内容。

F)Remove group read/write privileges from the private_key.pem file. [正确] 
private_key.pem权限为 rw-rw---- 表示同组用户有读写权限，私钥文件应严格限制访问。

E)Remove world read privileges from the server-cert.pem certificate file. [错误] 
移除server-cert.pem的全局读权限
证书文件（权限rw-r--r--）需被客户端读取，限制后会导致连接失败。

B)Remove world read privileges from the public_key.pem file. [错误] 
移除public_key.pem的全局读权限
公钥本身设计为可公开分发，无需限制读取（权限rw-r--r--已合理）。

C)Change the group ownership of the mysql directory to the mysql user group. [错误] 
修改 mysql 目录的组所有权为 mysql 用户组
无需更改。

试题21:

Choose two.Which two statements are true about general tablespaces? 
A)General tablespaces support temporary tables. [错误] 
B)Dropping a table from a general tablespace releases the space back to the operating system. [错误] 
C)An existing table can be moved into a general tablespace. [正确] 
E)A new table can be created explicitly in a general tablespace. [正确] 
D)A general tablespace can have multiple data files. [错误] 

解析

这道题和试题13一模一样,只是选项换了换。再来看下general 表空间的使用

A)General tablespaces support temporary tables. [错误] 
B)Dropping a table from a general tablespace releases the space back to the operating system. [错误] 
C)An existing table can be moved into a general tablespace. [正确] 
E)A new table can be created explicitly in a general tablespace. [正确] 
D)A general tablespace can have multiple data files. [错误] 


本题考查general表空间的使用
B)Dropping a table from a general tablespace releases the space back to the operating system. [错误]
从通用表空间删除表会释放空间回操作系统
错误：通用表空间的空间不会自动释放回操作系统
需要手动执行ALTER TABLESPACE … DROP DATAFILE来释放空间

D) 一个通用表空间可以有多个数据文件
错误：每个通用表空间只能有一个数据文件(.ibd文件)
但可以动态扩展这个数据文件的大小

A) 通用表空间支持临时表
错误：通用表空间不支持临时表
临时表只能存储在临时表空间或独立表空间中

E) 可以显式地在通用表空间中创建新表
使用CREATE TABLE … TABLESPACE tablespace_name语法
例如：CREATE TABLE t1 (id INT) TABLESPACE ts1;

C) 可以将现有表移动到通用表空间中
使用ALTER TABLE … TABLESPACE语法
例如：ALTER TABLE t1 TABLESPACE ts1;

试题22:

Choose three.Examine this command, which executes successfully:cluster.addInstance( ' 
<user>@<host>:<port>' , recoveryMethod:' clone ') 
Which three statements are true? 

D)The account used to perform this recovery needs the BACKUP_ADMIN privilege. [正确] 
E)A new instance is installed, initialized, and provisioned with data from an instance already in the 
cluster and joined to the cluster. [错误] 
B)InnoDB tablespaces outside the datadir are able to be cloned. [正确] 
C)A target instance must exist, then it will be provisioned with data from an instance already in the 
cluster and joined to the cluster. [正确] 
A)It is always slower than recoveryMethod:' incremental ' . [错误] 
F)InnoDB redo logs must not rotate for the duration of the execution; otherwise, the recovery will 
fail. [错误] 

解析

下是关于 cluster.addInstance() 使用 recoveryMethod: ‘clone’ 方法的三个正确选项及其解析：

D)The account used to perform this recovery needs the BACKUP_ADMIN privilege. [正确] 
执行此恢复操作的账户需要 BACKUP_ADMIN 权限

E)A new instance is installed, initialized, and provisioned with data from an instance already in the 
cluster and joined to the cluster. [错误] 
新实例会被安装、初始化并直接从集群中的实例克隆数据后加入集群
错误原因：clone 恢复方法 不会自动安装 MySQL 实例，仅适用于已存在但无数据的实例。

B)InnoDB tablespaces outside the datadir are able to be cloned. [正确] 
可以克隆位于 datadir 之外的 InnoDB 表空间
克隆操作会复制所有 InnoDB 表空间，包括使用 CREATE TABLESPACE 创建的通用表空间（即使不在默认数据目录内）。
例外：临时表空间（temporary tablespaces）不会被克隆。

C)A target instance must exist, then it will be provisioned with data from an instance already in the 
cluster and joined to the cluster. [正确] 
目标实例必须已存在，随后会从集群中的现有实例克隆数据并加入集群

A)It is always slower than recoveryMethod:' incremental ' . [错误] 
它总是比 recoveryMethod: 'incremental' 慢
错误原因：克隆速度取决于数据量，增量恢复（incremental）可能更慢（需应用大量 binlog）。

F)InnoDB redo logs must not rotate for the duration of the execution; otherwise, the recovery will fail. [错误] 
执行期间 InnoDB 重做日志不能轮转，否则恢复会失败
错误原因：克隆过程不依赖重做日志（redo log），而是直接复制数据文件，日志轮转不影响操作。

试题23:

Choose three.Which three sets of item information are visible in the mysql system database? 
G)information about table structures [错误] 
F)rollback segments [错误] 
E)performance monitoring information [错误] 
C)plugins [正确] 
D)audit log events [错误] 
B)help topics [正确] 
A)time zone information and definitions [正确]

解析

mysql 系统数据库中可以看到哪三组监控项信息？

G)information about table structures [错误] 
表结构信息
实际存储位置：表结构（元数据）存储在 information_schema 或 performance_schema 数据库，而非 mysql 库。

F)rollback segments [错误]
回滚段信息
实际存储位置：InnoDB 回滚段信息可通过 information_schema.innodb_trx 或 performance_schema 查看，与 mysql 库无关。
 
E)performance monitoring information [错误] 
性能监控信息
实际存储位置：性能数据主要在 performance_schema 或 sys 数据库，mysql 库不存储监控数据。

C)plugins [正确] 
mysql.plugin 表存储已安装的插件信息（如认证插件、存储引擎插件等）。

D)audit log events [错误] 
审计日志事件
实际存储位置：若启用审计日志，通常存储于专用文件或 audit_log 插件管理的表中，默认不在 mysql 库。

B)help topics [正确] 
mysql.help_topic 表包含 MySQL 内置的帮助文档内容（如 SQL 语法说明）。

A)time zone information and definitions [正确]
时区信息与定义 (time zone information)
mysql.time_zone* 系列表存储时区数据（需手动加载）
关键表：
    mysql.time_zone：时区名称
    mysql.time_zone_leap_second：闰秒信息
    mysql.time_zone_transition：时区转换规则

试题24:

Which two situations will cause the binary log to rotate? 
A)FLUSH HOSTS executed [错误] 
D)SET sql_ log bin-1 executed [错误] 
C)max_ binloq cache size exceeded [错误] 
B)max binlog_size exceeded [正确] 
F)FLUSH LOGS executed [正确] 
E)SET syne binlog-l executed1 [错误]

解析

哪两种情况会导致 binlog 切换？

A)FLUSH HOSTS executed [错误] 
执行 FLUSH HOSTS
清空主机缓存（如连接错误记录），与二进制日志无关。

D)SET sql_log bin-1 executed [错误] 
执行 SET sql_log_bin=0
临时禁用当前会话的二进制日志记录，不会触发轮换。

C)max_binlog cache size exceeded [错误] 
max_binlog_cache_size 超出限制
控制单个事务允许的最大缓存大小，超限会报错（Multi-statement transaction required more than 'max_binlog_cache_size'），但不会轮换日志文件。

B)max binlog_size exceeded [正确] 
当当前二进制日志文件大小达到 max_binlog_size 参数（默认 1GB）时，MySQL 会自动创建一个新的二进制日志文件。
注意：实际文件可能略微超过设定值，因为轮换仅在事务完成后触发。

F)FLUSH LOGS executed [正确] 
手动执行 FLUSH LOGS 会强制关闭当前二进制日志文件并立即创建一个新文件。

E)SET sync_binlog l executed1 [错误]
控制制二进制日志同步到磁盘的频率,不触发轮换

试题25:

Choose three.Which three statements are true about MySQL replication? 
D) Any instance can have multiple slaves, but it can have only one master. [错误] 
G) Binary logging must be enabled on the master in order to replicate to other instances. [正确] 
E) Binary logs contain only transactions originating from a single MySQL instance. [错误] 
F) Replication can use only TCP/IP connections. [正确] 
C) Each instance in a replication topology must have a unique server ID. [正确] 
A) Each slave must have its own MySQL user for replication. [错误] 
B) A replication user must have the SELECT privilege for all tables that need to be replicated. [错误]

解析

关于 MySQL 复制，哪三个陈述是正确的？

D) Any instance can have multiple slaves, but it can have only one master. [错误]
任何实例可以有多个从库，但只能有一个主库
错误原因：MySQL 支持多主复制（如环形复制、组复制），并非只能单主。 

G) Binary logging must be enabled on the master in order to replicate to other instances. [正确] 
主库必须启用二进制日志（Binary Log）才能复制到其他实例

E) Binary logs contain only transactions originating from a single MySQL instance. [错误] 
二进制日志仅包含来自单个 MySQL 实例的事务
错误原因：二进制日志记录所有数据变更，包括来自其他实例的中继事件（在级联复制中）。

F) Replication can use only TCP/IP connections. [正确] 
复制仅能使用 TCP/IP 连接，MySQL 复制默认通过 TCP/IP 协议通信，不支持 Unix Socket 或其他协议。

C) Each instance in a replication topology must have a unique server ID. [正确] 
复制拓扑中的每个实例必须具有唯一的 server ID
server_id 用于标识复制拓扑中的每个节点，必须全局唯一（否则导致数据混乱）。

A) Each slave must have its own MySQL user for replication. [错误] 
每个从库必须有自己的 MySQL 复制用户
错误原因：所有从库可共享同一个主库的复制账号（只需主库授权一次）。

B) A replication user must have the SELECT privilege for all tables that need to be replicated. [错误]
复制用户需要对所有复制的表具有 SELECT 权限
错误原因：复制用户仅需 REPLICATION SLAVE 权限，无需数据读取权限

未完，待续。后续题库会陆续发出，请关注。