tencent cloud

TDSQL Boundless

DocumentationTDSQL BoundlessUser GuideParameter ConfigurationParameter Configuration Recommendations

Parameter Configuration Recommendations

Download
Focus Mode
Font Size
Last updated: 2026-06-18 16:32:17
Depending on the customer's business scenarios, it is recommended to appropriately configure the following parameters after purchasing instances.

Parameter Configuration Overview

Parameter Name
Default Value
Whether Restart Required
Primary Function
Recommended Configuration
UTF8
Yes
Server default character set
Select based on business requirements.
STRICT_TRANS_TABLES,NO_ENGINE_SUBSTITUTION
No
SQL syntax and data validation rules
Configure based on business scenarios and development practices.
1
No
Slow query threshold time
Adjust based on customer business scenarios and performance sensitivity.
ON
No
DDL online replication mode switch
Keep enabled by default.
64MB
No
Single-row record size limitation
Keep the default configuration.
ON
No
Flashback query feature switch
It is recommended to enable.

Detailed Parameter Description

character_set_server

Default value: UTF8
Whether restart is required: Yes
Purpose: Configures the default character set for TDSQL Boundless servers.
Character Set
Characteristic
Scenarios
LATIN1
English characters, each character occupies one byte.
English-only application.
UTF8
International encoding contains characters needed by all countries worldwide.
One character occupies three bytes.
Multilingual support with strong versatility.
UTF8MB4
UTF8 superset, fully backward compatible, one character occupies four bytes.
Supports special characters such as emojis.
GBK
Double-byte character set, meaning that regardless of Chinese or English characters, all are represented using two bytes.
Simplified Chinese environment.
GB18030
The latest national standard Chinese character set, which is a superset of GBK, includes all characters of GBK and additionally supports more Chinese characters and Chinese minority scripts.
Comprehensive Chinese character support.
UJIS
Japanese encoding. English characters occupy one byte, while Japanese characters (kanji, kana, and so on) occupy two bytes.
Limited to Japanese environments, especially for compatibility with legacy Japanese systems.
Recommendation: After purchasing an instance, select an appropriate character set based on the data formats required by your business. Ensure consistent character set settings between client and server to prevent garbled text issues and unnecessary restarts caused by incorrect configurations.

sql_mode

Default value: STRICT_TRANS_TABLES,NO_ENGINE_SUBSTITUTION
Whether it needs to be restarted: No
Note:
The default value of sql_mode in TDSQL Boundless differs from that of MySQL 8.0, adopting a more lenient configuration. The default parameter value for MySQL 8.0 is ONLY_FULL_GROUP_BY, STRICT_TRANS_TABLES, NO_ZERO_IN_DATE, NO_ZERO_DATE, ERROR_FOR_DIVISION_BY_ZERO, NO_ENGINE_SUBSTITUTION. TDSQL Boundless does not enable date validation (such as NO_ZERO_DATE) and strict GROUP BY checking, offering better compatibility but looser data validation. For stricter data validation, manually adjust sql_mode.
Purpose: TDSQL Boundless can operate under different SQL modes, which define the SQL syntax and data validation that should be supported. The default parameter value for TDSQL Boundless is set to STRICT_TRANS_TABLES, NO_ENGINE_SUBSTITUTION. Among these:
STRICT_TRANS_TABLES enables strict mode for transactional tables, controlling how invalid or missing data values are handled. If invalid values are inserted, such as out-of-range values, excessively long strings, or missing values in NOT NULL columns, the strict mode for transactional tables reports an error and rejects the operation. The NO_ZERO_IN_DATE, NO_ZERO_DATE, and ERROR_FOR_DIVISION_BY_ZERO modes define what constitutes invalid data, while STRICT_TRANS_TABLES defines how to handle such invalid data when it is encountered.
NO_ZERO_IN_DATE controls whether months and days in dates can contain zero, and this is affected by whether strict mode is enabled.
NO_ZERO_DATE disallows inserting zero dates into the database, and this behavior is affected by whether strict mode is enabled.
ERROR_FOR_DIVISION_BY_ZERO In strict mode, if data is divided by zero during INSERT or UPDATE operations, an error is generated instead of a warning. In non-strict mode, NULL is returned when division by zero occurs.
ONLY_FULL_GROUP_BY indicates that in GROUP BY aggregation operations, columns in the SELECT, HAVING, or ORDER BY clauses must either appear in the GROUP BY clause or be functional dependencies of the GROUP BY columns.
Note:
Adjustments to the sql_mode parameter take effect globally. However, note that for the ONLY_FULL_GROUP_BY configuration within its parameter values, if an old connection is persistent, the change remains session-level. Therefore, after the ONLY_FULL_GROUP_BY configuration is modified, it takes effect for new connections, but may not apply to existing ones until they are disconnected and reconnected.
NO_AUTO_CREATE_USER forbids GRANT from creating users with empty passwords.
NO_ENGINE_SUBSTITUTION throws an error if the storage engine used is disabled or not compiled.
Recommendation: Since different SQL modes support different SQL syntaxes, it is recommended to configure appropriately based on your business scenarios and development practices.

long_query_time

Default value: 1
Whether it needs to be restarted: No
Purpose: Used to specify the threshold time for slow queries, with a default value of 1s. When a query execution time is 1s or more, the execution details of that query are recorded in the slow log to facilitate subsequent analysis of slow queries.
Recommendation: As customer business scenarios and performance sensitivity vary, it is recommended to set appropriate values based on specific business contexts to facilitate subsequent performance analysis.

tdsql_use_online_copy_ddl

Default value: ON
Whether it needs to be restarted: No
Purpose: Controls whether to enable the DDL online replication mode for TDSQL Boundless.
ON (default): After the DDL online replication mode is enabled, DDL operations do not lock tables and do not block business read and write operations.
OFF: Disable DDL online replication mode, which will fall back to MySQL's native Copy DDL. This means that during the execution of non-Inplace or non-Instant DDL, write requests to the table will be blocked.
Recommendation: Keep the default configuration, enabled by default. If errors occur during operations such as adding/dropping primary keys, adding a column with an expression as a default value (ADD COLUMN DEFAULT (a+a)), or altering tables with triggers, you can temporarily disable Online DDL mode by executing set tdsql_use_online_copy_ddl = 0, then retry.
Note:
After temporarily disabling it, the setting must be immediately restored to ON to prevent subsequent DDL operations from unexpectedly blocking business operations.
The temporary disabling operation should be performed within the same transaction or connection session to ensure the consistency of the settings.

tdstore_txn_max_entry_size

Default value: 67108864
Whether it needs to be restarted: No
Purpose: Controls the size of a single-row record, with a default of 64MB. When the size of a single-row record being written exceeds 64MB, the statement execution will fail.
Recommendation: Keep the default configuration. If the single-row record size exceeds 64MB, contact Tencent Cloud technical support to evaluate and adjust.

tdsql_enable_stale_read

Default value: ON
Whether it needs to be restarted: No
Purpose: Controls the flashback query feature switch.
Recommendation: Recommend enabling the flashback query feature by default to facilitate quickly querying historical versions of data and performing recovery in scenarios of accidental updates.
Previous Topic: Setting Instance ParametersNext Topic: Parameter Templates

Help and Support

Was this page helpful?

Help us improve! Rate your documentation experience in 5 mins.

Feedback