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Updated on 2025-01-26 GMT+08:00
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Suggestions on Parameter Tuning for a FlexusRDS for MySQL Instance

Parameters are key configuration items in a database system. Improper parameter settings may adversely affect database performance. This section describes some important parameters for your reference. For details, visit the MySQL official website.

For details on how to modify FlexusRDS parameters on the console, see Modifying Parameters of a FlexusRDS for MySQL Instance.

Sensitive Parameters

  • innodb_flush_log_at_trx_commit

    Default value: 1

    Function: Controls the balance between strict ACID compliance for commit operations and higher performance. The default setting of 1 is required for full ACID compliance. Logs are written and flushed to disks at each transaction commit. If the value is set to 0, logs are written and flushed to disks once per second. If the value is set to 2, logs are written at each transaction commit and flushed to disks every two seconds.

    Impact: If this parameter is not set to 1, data security is not guaranteed. If the system fails, data may be lost.

    Recommended value for POC: 2

  • sync_binlog

    Default value: 1

    Function: Controls how often the MySQL server synchronizes binary logs to the disk. The default setting of 1 requires synchronization of the binary log to the disk at each transaction commit. If the value is set to 0, synchronization of the binary log to the disk is not controlled by the MySQL server but relies on the OS to flush the binary log to the disk. This setting provides the best performance. However, if a power failure occurs or the OS crashes, all binary log information in binlog_cache will be lost.

    Impact: If this parameter is not set to 1, data security is not guaranteed. If the system fails, binary logs may be lost.

    Recommended value for POC: 1000

  • innodb_buffer_pool_size

    Default value: Varies depending on the DB instance classes.

    Function: Specifies the size of the InnoDB buffer pool. The InnoDB buffer pool is used to cache table and index data. Increasing the value of this parameter reduces disk I/O.

    Impact: Setting this parameter to a large value may cause system breakdown. Exercise caution when changing this parameter value.

    Recommended value for POC: 70% to 75% of the memory for your DB instances with 32 GB memory or above

Performance Parameters

  • The values of innodb_spin_wait_delay and query_alloc_block_size are determined by the DB instance specifications. If you increase their values, database performance may be affected.
  • max_connections: indicates the total number of clients that can be concurrently connected. The default value of this parameter depends on the system architecture. System built-in connections occupy some connections specified by this parameter. To prevent concurrent connection conflicts, you are advised not to set this parameter to a value less than 30. This parameter cannot be set to a value smaller than the number of current connections.
  • The default values of the following parameters are determined by the DB instance specifications: innodb_buffer_pool_size, max_connections, and back_log. These parameter values are default before being specified.
  • The values of innodb_io_capacity_max and innodb_io_capacity are determined by the storage type. These parameter values are default before being specified.

Associated Parameters

  • character_set_server: If you change the value of this parameter, the system changes the value of collation_server accordingly.

    The parameters character_set_server and collation_server are correlated with each other. For example, for MySQL 5.7, when character_set_server is latin1, the default value of collation_server is latin1_swedish_ci. The collation_server value must start with latin1.

  • innodb_io_capacity: The value of this parameter must be less than or equal to the value of innodb_io_capacity_max. For example, if innodb_io_capacity_max is set to 2000, the maximum value of innodb_io_capacity is 2000.

Constraints on Parameter Modification

  • When the innodb_adaptive_hash_index and innodb_buffer_pool_size parameters are modified at the same time, the value of innodb_adaptive_hash_index will fail to be changed from OFF to ON.
  • If innodb_buffer_pool_instances is set to 2, the value of innodb_buffer_pool_size must be greater than or equal to 1 (unit: GB).

Other Parameters

  • max_prepared_stmt_count: limits the upper limit of prepared statements. Too many prepared statements consume server memory resources. If this parameter is set to a small value, your DB instance may be vulnerable to the denial of service (DoS) attacks. You are advised to change this parameter value based on service requirements.
  • The values of the following parameters will be adjusted based on kernel rules:
    • key_cache_age_threshold: automatically adjusted to a multiple of 100.
    • join_buffer_size and key_cache_block_size: automatically adjusted to multiples of 128.
    • query_prealloc_size, innodb_log_buffer_size, max_allowed_packet, and thread_stack: automatically adjusted to multiples of 1024.
    • read_buffer_size, read_rnd_buffer_size, binlog_cache_size, and binlog_stmt_cache_size: automatically adjusted to multiples of 4096.
  • innodb_strict_mode: restricts the InnoDB check policy. The default value is OFF.
  • binlog_rows_query_log_events: controls whether to write original SQL statements into binlogs. If this parameter is set to ON, database performance may deteriorate when a large amount of data is updated. Before you change the parameter value, consider the compatibility with tools such as Otter.
Parent topic: Parameters