The Repeatable Read level prevents dirty reads but allows phantom reads, which means another transaction can insert new rows before a query is re-executed. Read Uncommitted allows dirty reads, Serializable blocks phantoms, and Read Committed allows non-repeatable reads.

If the configured keyring plugin is unavailable, encrypted tables will remain unreadable since the encryption keys cannot be retrieved. MySQL does not have a fallback encryption mechanism or temporary session-based keys for tablespaces.

To change a user’s authentication plug-in, use ALTER USER ‘user‘@‘host‘ IDENTIFIED WITH plugin. Using ALTER USER … IDENTIFIED BY changes the password but not the authentication plug-in. ALTER USER … USING is invalid syntax. Directly modifying mysql.user is not recommended, as changes do not apply until a restart.

mysqldump is the primary MySQL tool for performing logical backups by generating SQL statements that can recreate the database. mysqlpump is a parallelized version of mysqldump for faster exports. mysqlbackup (part of MySQL Enterprise) and xtrabackup (by Percona) perform physical backups rather than logical ones.

To ensure data consistency, MySQL must be stopped before taking a raw file backup, preventing corrupt or incomplete copies. Logging is unnecessary. Binary logs do not affect raw backups directly, and system tables are included in the data directory.

In multi-primary group replication, multiple nodes can write simultaneously, but conflicts can occur if the same data is modified in multiple locations, requiring automatic conflict resolution strategies.

The audit_log_rotate_on_size variable controls when MySQL rotates the audit log file based on size limits. Other options do not exist in MySQL 8.0.

The InnoDB Change Buffer caches modifications to secondary indexes (INSERT, UPDATE, DELETE) before writing them to disk. This improves performance by batching index changes rather than updating the indexes immediately. It does not store execution plans, dirty pages, or undo logs.

The Enterprise Monitor Repository is responsible for storing collected monitoring data, enabling historical performance analysis. Other options relate to event logging, performance schema tracking, and audit logging, but they do not store monitoring metrics.

A user account with no password and access from any host (‘%‘) allows unauthorized access, making it a severe security vulnerability. Using localhost with a strong password is secure, requiring SSL on a private network is safer, and auth_pam allows integration with external authentication, reducing risk.

MySQL 8.0 changed its default authentication plugin to caching_sha2_password, requiring manual client updates. Other settings do not require mandatory changes.

The audit_log plugin is responsible for capturing and enforcing audit logging policies in MySQL. The log_output setting controls log destinations but is unrelated to auditing. The binlog_format option determines binary logging, while the performance_schema does not store audit logs.

Group Replication provides synchronous replication ensuring strong consistency across all nodes. It does not use asynchronous replication, load balance queries, or store data in memory (though InnoDB may cache data).

The skip-grant-tables option disables MySQL’s authentication system, allowing root access without a password. This is useful for emergency recovery but should not be enabled in a production system. authentication_policy manages password complexity rules, default_authentication_plugin sets the default authentication method, and use_native_passwords is not a valid MySQL variable.

A Physical Backup is significantly faster because it copies raw files, whereas a Logical Backup requires SQL parsing during restore. Logical backups are more portable and support partial restores, while physical backups require system-level privileges.

Row-based replication (RBR) ensures that transactions are committed in the exact order they were executed on the source server by replicating the actual row changes instead of the SQL statements. This prevents issues like non-deterministic behavior that can occur with statement-based replication (SBR), where certain functions (such as UUID or RAND) might produce different results on the replica. Mixed replication switches between SBR and RBR but does not guarantee strict ordering in all cases. Asynchronous replication does not affect the replication method itself but determines how updates are delivered from the source to the replica.

When skip_name_resolve is enabled, MySQL does not resolve hostnames to IP addresses, and all client authentication must use IP-based user accounts rather than hostnames. This improves connection performance by avoiding DNS lookups. It does not enforce encryption or modify query execution speed.

The –quick-buffer-mode option tells mysqldump to fetch rows one by one, reducing memory usage and improving performance on large tables. –stream-dump-option is not valid. –skip-lock-backups does not exist, and –no-create-database omits database creation statements.

To restart MySQL without stopping it first, use systemctl restart mysqlserver. The other options contain incorrect systemd syntax or reference non-existent commands.

The Retrieved_Gtid_Set value shows transactions fetched by the I/O thread but not yet applied by the SQL thread. The executed GTIDs are in a different status variable, and GTIDs in relay logs or binary logs are not exclusive to unexecuted transactions.

The mysql.routines table stores metadata for stored procedures and functions inside the Data Dictionary. The other options do not exist or serve different purposes.

The log_error variable determines where MySQL writes its error log, crucial for troubleshooting. The binary log is controlled by log_bin, while log_output manages log destinations but not the error log itself.

The MySQL Performance Schema is a diagnostic tool that collects low-level performance data, including query execution times, wait events, and resource usage. By analyzing this data, administrators can identify bottlenecks and optimize database performance. Unlike regular tables, Performance Schema tables do not store historical query results but instead provide real-time monitoring. Indexing improves query speed but is unrelated to Performance Schema, and user privilege management is handled by the mysql system database.

To restore raw file backups on another server, the MySQL version must match, files must be copied correctly, and the server must be restarted. Reconfiguring indexes or importing schema is unnecessary, as raw backups copy full data files.

To remove a role from a user, use REVOKE ‘role_name‘ FROM ‘user‘@‘host‘. REMOVE and DELETE ROLE are not valid MySQL commands, and DROP ROLE deletes the role entirely instead of just removing it from the user.

group_replication_exit_state_action controls what happens when a node fails to apply transactions, allowing options like ABORT_SERVER or READ_ONLY. Replay buffers, checkpoints, and conflict handlers are not responsible for transaction failures.

By redirecting read queries to replicas, replication offloads workload from the primary server, improving scalability for read-heavy applications. However, replicas do not handle writes unless additional mechanisms like multi-primary replication are used.

binlog_expire_logs_seconds controls how long MySQL retains binary logs before automatically deleting them. innodb_log_file_size_value defines InnoDB log file size, slow_query_log_threshold sets logging limits, and sync_binlog_auto_commit does not control retention.

MySQL stores its data files in /var/lib/mysql_database by default on Linux systems. The other options are incorrect directory paths that do not exist in MySQL installations.

The default location for InnoDB system tablespace files is /var/mysql/innodb-systemdata/, unless otherwise configured. The other options refer to incorrect or non-existent directories.

The Redo Log Write-Ahead Mechanism guarantees data durability by ensuring changes are first written to logs before being flushed to disk. Full Page Writes prevent corruption, Buffer Pool Flush handles page eviction, and Index Merging optimizes indexes.

The mysqldump –database-dump utility exports MySQL databases as SQL files for backup or migration. The other options reference non-existent MySQL utilities.

The ROW format logs exact row changes, ensuring consistent replication. STATEMENT-based logs may cause non-deterministic issues. MIXED tries to combine both, but row-based logs are preferred for backups. COMPRESSED is not a valid format.

The –ssl-mode=REQUIRED option ensures that MySQL establishes a secure connection using SSL/TLS. If the server does not support encryption, the connection fails. The other options are not valid MySQL connection parameters for enforcing SSL.

MySQL 8.0 removes old authentication plugins, requiring client updates. Redo logs, binary log truncation, or forced engine conversion are not upgrade risks.

The best practice for managing multiple MySQL instances with systemd is to create separate unit files for each instance. Each unit file specifies unique configurations such as data directory, port, and socket. Modifying my.cnf alone is insufficient because it typically defines a single instance. Running instances with different user accounts is unnecessary, and starting instances manually lacks automation and reliability.

InnoDB benefits the most from raw file backups because it supports transaction consistency and can handle crash recovery. MEMORY tables are lost on restart. ARCHIVE and CSV do not benefit from raw file backups, as they do not use standard data files.

Setting require_secure_transport=ON forces all MySQL client connections to use SSL/TLS encryption, ensuring data confidentiality. The other options do not exist in MySQL 8.0.

The sp_reload_firewall_rules procedure is used to reset MySQL Enterprise Firewall rules for a specific user. The other commands are either invalid or do not exist in MySQL.

The innodb_buffer_pool_size is configured in the [mysqld] section, which applies to server-level settings. Other sections, such as innodb or client, are not used for this setting.

MySQL Router transparently directs traffic to healthy nodes, ensuring high availability. It does not synchronize transactions, validate consistency, or manage conflicts, which are handled by Group Replication mechanisms.

The relay log temporarily stores replicated transactions from the primary before execution on the replica, ensuring data consistency while tracking replica execution progress.

B-tree indexes are ideal for range queries because they allow efficient traversal over ranges of values. Hash, spatial, and full-text indexes are optimized for different types of queries.

On Windows, the MySQL service is started with net start mysqlserver. The other options contain incorrect MySQL service names or do not exist.

Running FLUSH LOGS before a backup creates a new binary log file, ensuring a clear starting point for recovery. RESET MASTER deletes all logs, which is dangerous. sync_binlog improves durability but does not force log rotation. ANALYZE TABLE is unrelated.

The binary log records changes to tables, ensuring replication and point-in-time recovery. The error log logs startup issues. The general log captures all queries, while the slow query log tracks long-running queries.

To create a new MySQL instance, the mysqld –initialize command sets up a fresh data directory with system tables. mysqladmin is used for administrative tasks, mysql_secure_installation configures security settings, and mysqld_safe is a wrapper script for starting MySQL but does not initialize a data directory.

The default_password_lifetime setting enforces automatic password expiration, requiring users to change their passwords periodically. The other options do not exist in MySQL 8.0.

The EXPLAIN ANALYZE command provides detailed execution plans, revealing if an index is used in a query. SHOW DATABASES lists databases, not execution plans. OPTIMIZE TABLE is used for table maintenance, not query performance. FLUSH PRIVILEGES reloads user privileges but does not relate to index usage.

The password_lock_time system variable defines the lockout duration after multiple failed login attempts. password_expire_interval controls password expiration, account_locked_duration is incorrect syntax, and failed_login_attempts_limit does not exist in MySQL 8.0.

The SQL thread in MySQL reads the relay log and executes transactions in the same order as recorded in the binary log. It does not coordinate replication sources, monitor network traffic, or fetch binary logs (which is the job of the I/O thread).

The Time-Series Graphs in MySQL Enterprise Monitor provide historical insights into query execution times, CPU usage, memory utilization, and connection trends. Other options do not provide a historical view.

The my.cnf file is the primary configuration file used by MySQL on Linux systems. The other files either provide defaults or are platform-specific but are not used for startup configurations.

Multi-threaded replication allows replicas to apply transactions in parallel, reducing replication lag and improving performance for high-throughput workloads.

The max_connect_errors variable defines the number of failed connection attempts allowed before MySQL temporarily blocks the offending IP address. This prevents brute-force attacks. To reset blocked hosts, administrators can run FLUSH HOSTS. The other options are either nonexistent or related to different security mechanisms.

Indexes on foreign key columns can significantly speed up JOINs by allowing MySQL to quickly locate matching rows. Other factors, like primary keys or disabling query cache, are less impactful.

The Clone Plugin enables fast and efficient cloning of an existing MySQL instance to create a new one, making it ideal for deploying multiple instances with similar configurations. Binary Logging supports replication but does not create new instances. Replication Filters control data flow in replication, and Delayed Transactions allow postponed commits but are unrelated to instance deployment.

Group Replication uses certification-based conflict detection, which verifies transactions before committing to ensure consistency across all nodes. Redo logs are used for crash recovery, table-level locking is inefficient for replication, and statement-based logging can cause non-deterministic execution issues.

A high Handler_read_rnd_next count indicates many sequential row reads, suggesting full table scans instead of index usage. Low Innodb_buffer_pool_size affects caching but does not directly show index inefficiency. Query_cache_hits relates to caching, and Threads_running refers to concurrent queries.

Each additional index increases storage requirements and maintenance overhead. While indexes improve SELECT performance, they slow down INSERT, UPDATE, and DELETE operations because MySQL must update multiple index structures. Indexes do not reduce transaction isolation, nor do they inherently decrease SELECT speed unless over-indexing leads to inefficient execution plans.