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User Guide
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Instance Management
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Parameter Template Management
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Data Migration
- Overview
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- Scenario 1: Migrating Data from an On-Premises MySQL Instance to DDM
- Scenario 2: Migrating Data from a Third-Party Cloud MySQL Instance to DDM
- Scenario 3: Migrating Data from an ECS-hosted MySQL Instance on Huawei Cloud to DDM
- Scenario 4: Exporting Data from a DDM Instance
- Scenario 5: Migrating Data from Heterogeneous Databases to DDM
- Scenario 6: Migrating Data from Huawei Cloud RDS for MySQL to DDM
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SQL Syntax
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API Reference
- Before You Start
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APIs (Recommended)
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DDM Instances
- Buying a DDM instance
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- Modifying the Name of a DDM Instance
- Changing the Security Group of a DDM Instance
- Deleting a DDM Instance
- Restarting a DDM Instance
- Reloading Table Data
- Scaling Out a DDM Instance
- Scaling in a DDM instance
- Modifying the Read Policy of the Associated DB Instance
- Synchronizing Data Node Information
- Querying Nodes of a DDM Instance
- Querying Details of a DDM Instance Node
- Querying Parameters of a Specified DDM Instance
- Modifying Parameters of a DDM Instance
- Querying DDM Engine Information
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DDM Instances
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Best Practices
- Overview
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- Migrating an Entire RDS Database to DDM
- Migrating an Entire MyCat Database to DDM
- Accessing DDM Using a JDBC Connection Pool
- Logging In to a DDM Instance Using Navicat
- Migrating Data from RDS for MySQL to DDM Using DRS
- Sharding Database and Table Data of an RDS for MySQL Instance
- Performance White Paper
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FAQs
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DDM Usage
- How Does DDM Perform Sharding?
- What Do I Do If I Fail to Connect to a DDM Instance Using the JDBC Driver?
- Why It Takes So Long Time to Export Data from MySQL Using mysqldump?
- What Do I Do If a Duplicate Primary Key Error Occurs When Data Is Imported into DDM?
- What Should I Do If an Error Message Is Returned When I Specify an Auto-Increment Primary Key During Migration?
- What Do I Do If an Error Is Reported When Parameter Configuration Does Not Time Out?
- Which Should I Delete First, a Schema or its Associated RDS Instances?
- Can I Manually Delete Databases and Accounts Remained in Data Nodes After a Schema Is Deleted?
- SQL Syntax
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RDS-related Questions
- Is the Name of a Database Table Case-Sensitive?
- What Risky Operations on RDS for MySQL Will Affect DDM?
- How Do I Handle Data with Duplicate Primary Keys in a Table?
- How Can I Query RDS for MySQL Information by Running Command show full innodb status?
- What Should I Pay Attention to When Selecting RDS for MySQL Instance Specifications?
- Connection Management
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- Videos
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More Documents
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User Guide (ME-Abu Dhabi Region)
- Service Overview
- Getting Started
- Function Overview
- Instance Management
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Parameter Template Management
- Creating a Parameter Template
- Editing a Parameter Template
- Comparing Two Parameter Templates
- Viewing Parameter Change History
- Replicating a Parameter Template
- Applying a Parameter Template
- Viewing Application Records of a Parameter Template
- Modifying the Description of a Parameter Template
- Deleting a Parameter Template
- Task Center
- Schema Management
- Account Management
- Backup Management
- Monitoring Management
- Auditing
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SQL Syntax
- Introduction
- DDL
- DML
- Functions
- Unsupported Items
- Supported SQL Statements
- Global Sequence
- Database Management Syntax
- Advanced SQL Functions
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FAQs
- General Questions
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DDM Usage
- How Can I Rectify a Fault in Accessing DDM by Using the JDBC Driver?
- What Version and Parameters Should I Select?
- Why It Takes So Long Time to Export Data from MySQL Using mysqldump?
- How Should I Handle the Duplicate Primary Key Error Occurring After Data Is Imported into DDM?
- What Should I Do If an Error Message Is Returned After I Specify an Auto-Increment Primary Key?
- How Do I Handle the Error Reported When Parameter Configuration Does Not Time Out?
- Which Should I Delete First, Schema or Associated RDS DB Instances?
- Should I Manually Delete Databases and Accounts Remained in the Associated RDS DB Instances After a Schema Is Deleted?
- SQL Syntax
- RDS-related Questions
- Connection Management
-
User Guide (Kuala Lumpur Region)
- Service Overview
- Getting Started
- Function Overview
- Instance Management
-
Parameter Template Management
- Creating a Parameter Template
- Editing a Parameter Template
- Comparing Two Parameter Templates
- Viewing Parameter Change History
- Replicating a Parameter Template
- Applying a Parameter Template
- Viewing Application Records of a Parameter Template
- Modifying the Description of a Parameter Template
- Deleting a Parameter Template
- Task Center
- Schema Management
- Account Management
- Backup Management
- Monitoring Management
- Auditing
-
SQL Syntax
- Introduction
- DDL
- DML
- Functions
- Unsupported Items
- Supported SQL Statements
- Global Sequence
- Database Management Syntax
- Advanced SQL Functions
-
FAQs
- General Questions
-
DDM Usage
- How Can I Rectify a Fault in Accessing DDM by Using the JDBC Driver?
- What Version and Parameters Should I Select?
- Why It Takes So Long Time to Export Data from MySQL Using mysqldump?
- How Should I Handle the Duplicate Primary Key Error Occurring After Data Is Imported into DDM?
- What Should I Do If an Error Message Is Returned After I Specify an Auto-Increment Primary Key?
- How Do I Handle the Error Reported When Parameter Configuration Does Not Time Out?
- Which Should I Delete First, Schema or Associated RDS DB Instances?
- Should I Manually Delete Databases and Accounts Remained in the Associated RDS DB Instances After a Schema Is Deleted?
- SQL Syntax
- RDS-related Questions
- Connection Management
-
API Reference (Kuala Lumpur Region)
- Before You Start
- API Overview
- Calling APIs
-
DDM Instance Management
- Querying DDM Engine
- Querying the Quota of Classes Available in Each AZ
- Creating a DDM Instance
- Querying DDM Instances
- Viewing Details of a DDM Instance
- Modifying the Name of a DDM Instance
- Modifying the Security Group of a DDM Instance
- Deleting a DDM Instance
- Restarting a DDM Instance
- Reloading Table Data
- Scaling Out a DDM instance
- Scaling In a DDM instance
- Modifying the Read Policy of the Associated DB Instance
- Synchronizing DB Instance Data
- Querying Nodes of a DDM Instance
- Querying Details of a DDM Instance Node
- Querying Parameters of a Specified DDM Instance
- Modifying Parameters of a DDM Instance
- Schema Management
- Account Management
- Monitoring Management
- Permissions Policies and Supported Actions
- Appendix
- Change History
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User Guide (ME-Abu Dhabi Region)
- General Reference
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Instance Parameters
By default, DDM allows you to modify only the following parameters. If you need to modify other parameters in some special scenarios, such as data migration, contact technical support.
Parameter |
Description |
Value Range |
Default Value |
---|---|---|---|
bind_table |
Data association among multiple sharded tables. The optimizer processes JOIN operations at the MySQL layer based on these associations. For details about parameter examples, see the description below the table. |
- |
|
character_set_server |
DDM server's character set. To store emoticons, set both this parameter and the character set on RDS to utf8mb4. For a DDM instance 3.0.9 or later, you can execute show variables like '%char%' to query its character set. You will find that character_set_client, character_set_results, and character_set_connection in the command output all have a fixed value, utf8mb4. |
gbk, utf8, utf8mb4 |
utf8mb4 |
collation_server |
Collation on the DDM server. |
utf8mb4_unicode_ci, utf8mb4_bin, utf8mb4_general_ci |
utf8mb4_unicode_ci |
concurrent_execution_level |
Concurrency level of scanning table shards in a logical table:
|
RDS_INSTANCE, DATA_NODE, PHY_TABLE |
DATA_NODE |
connection_idle_timeout |
Number of seconds the server waits for activity on a connection before closing it. The default value is 28800, indicating that the server waits for 28,800 seconds before closing a connection. |
60~86400 |
28800 |
contains_shard_key |
Whether the SELECT, UPDATE, and DELETE statements must contain sharding keys in filter conditions. |
OFF or ON |
OFF |
ddl_precheck_mdl_threshold_time |
Threshold of the MDL duration in DDL pre-check. The unit is second. The default value is 120. |
1~3600 |
120 |
enable_table_recycle |
After the table recycle bin is enabled, deleted tables are moved to the recycle bin and can be recovered by running the RESTORE command within seven days. |
OFF or ON |
OFF |
long_query_time |
Minimum duration of a query to be logged as slow, in seconds. The default value is 1, indicating that the query is considered as a slow query if its execution duration is greater than or equal to 1 second. |
0.01~10 |
1 |
max_allowed_packet |
Maximum size allowed for the packets transferred between the server and the client at a time. The value must be a multiple of 1024. |
1024~1073741824 |
1073741824 |
max_backend_connections |
Maximum of concurrent client connections allowed per DDM instance. When this parameter is set to 0 (default), the maximum concurrent connections from a DDM node to an RDS instance is: (RDS instance's maximum connections - 20)/DDM nodes. This parameter does not take effect only after maximum connections are set on RDS. |
0~10000000 |
0 |
max_connections |
Minimum concurrent connections from a DDM instance node to the client. This value depends on node classes and processing capabilities of the target data node. Too many connections may cause connection waiting, affecting performance. The consumption of DDM connections varies with the number of shards and SQL design. For example, If a SQL statement contains a sharding key, each DDM connection consumes one data node connection. If the SQL statement contains no sharding keys and the number of shards is N, N data node connections are consumed. If SQL design is appropriate and processing capabilities of DDM and its data nodes are good enough, you can set this parameter to a value slightly smaller than the product of backend data nodes x maximum connections supported by each data node. Carry out pressure tests on your services and then select a proper value. |
10~40000 |
20000 |
min_backend_connections |
Minimum of concurrent client connections allowed per DDM instance. The default value is 10. |
0~10000000 |
10 |
seconds_behind_master |
Threshold in seconds of the replication lag between a primary RDS instance to its read replica. The default value is 30, indicating that the time for data replication between the primary RDS instance and its read replicas cannot exceed 30 seconds. If the time exceeds 30 seconds, the data read requests are no longer forwarded to the read replicas. |
0~7200 |
30 |
sql_execute_timeout |
Number of seconds to wait for a SQL statement to execute before it times out. The default value is 28800, indicating that the SQL statement times out if its execution time is greater than or equal to 28,800 seconds. For data nodes, ensure that net_write_timeout has a greater value than sql_execute_timeout. |
100~28800 |
28800 |
temp_table_size_limit |
Size of a temporary table. |
500000~2000000000 |
1000000 |
transfer_hash_to_mod_hash |
Whether the hash algorithm must be converted into mod_hash during table creation. |
OFF or ON |
OFF |
ultimate_optimize |
Whether the SQL execution plan is optimized based on parameter values. |
OFF or ON |
ON |
force_read_master_in_transaction |
Whether SQL statements involved in each transaction are read from the master node.
CAUTION:
This parameter is available in version 3.0.9 or later. If this feature is enabled in version 3.0.9 but the version is downgraded to 3.0.9 below, the feature keeps enabled when the version returns to 3.0.9 or later. |
OFF or ON |
OFF |
ddl_flowcontrol_threshold |
Maximum number of DDL executions (including successful and failed executions) allowed per hour. |
1000~100000 |
10000 |
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