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Instance Management
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Parameter Template Management
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Data Migration
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- 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
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APIs (Recommended)
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DDM Instances
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- 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
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- 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
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- Performance White Paper
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FAQs
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DDM Usage
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- What Do I Do If I Fail to Connect to a DDM Instance Using the JDBC Driver?
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- 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?
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More Documents
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User Guide (ME-Abu Dhabi Region)
- Service Overview
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- 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
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- 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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Parameter Management
Scenarios
Configure parameters of a DDM instance based on your needs to keep the instance running well.
Prerequisites
There is a DDM instance available and running properly.
Procedure
- Log in to the DDM console.
- In the navigation pane, choose Instances.
- In the instance list, locate the DDM instance whose parameters you want to configure and click its name.
- In the left pane, click Parameters and modify parameter values as needed.
Figure 1 Parameter management page
Table 1 Parameters of a DDM instance Parameter
Default Value
Value Range
Description
bind_table
-
The value should be in format [{tb.col1,tb2.col2},{tb.col2,tb3.col1},...]. tb.col1,tb2.col2 indicates a table name.column name pair, and the value may contain multiple pairs.
The version should be:
DDM 2.3.2.7 or later
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.
max_connections
20000
10–40000
Maximum number of concurrent client connections allowed per DDM instance.
This value depends on specifications and processing capabilities of the target RDS MySQL DB instance. Too many connections may cause connection waiting, affecting performance. The consumption of DDM connections is related to the number of shards and SQL design.
For example, If a SQL statement contains a sharding key, each DDM connection consumes one RDS MySQL instance connection. If the SQL statement contains no sharding key and the number of shards is N, N RDS MySQL connections are consumed.
If SQL design is appropriate and DDM and RDS processing capabilities are good enough, you can set this parameter to a value slightly smaller than "backend RDS MySQL DB instances" x "maximum connections supported by each RDS MySQL DB instance".
Carry out pressure tests on your services and then select a proper value.
connection_idle_timeout
28800
60–86400 (s)
Number of seconds the server waits for activity on a connection before closing it.
long_query_time
1
0.1–3600 (s)
Minimum duration of a query to be logged as slow.
sql_execute_timeout
28800
100–28800 (s)
Number of seconds to wait for a SQL statement to execute before timing out.
connection_failed_threshold
50
1–10000
Number of consecutive failed connection attempts allowed before your account and IP address are locked.
connection_failed_delay
1200
1–86400
Number of seconds before a locked account and IP address are unlocked.
max_allowed_packet
16777216
1024–1073741824
Maximum size of one packet or any generated intermediate string. The packet message buffer is initialized to net_buffer_length bytes, but can grow up to max_allowed_packet bytes when needed. The value is small by default. You need to set a larger value to catch large (and possibly incorrect) packets. The value must be a multiple of 1024.
character_set_server
utf8
gbk, utf8, utf8mb4
Character set configured on the DDM instance. To store emoticons, set both this parameter and the character set on the RDS MySQL DB instance to utf8mb4.
NOTE:
The character sets of the DDM instance and RDS MySQL DB instance must be consistent, including values of parameters character_set_client, character_set_connection, character_set_database, character_set_results, and character_set_server.
collation_server
The parameter value range is based on the character_set_server value.
The parameter value range is based on the character_set_server value.
Collation on the DDM server.
You need to configure this parameter after configuring character_set_server as follows:
- If character_set_server is set to gbk, collation_server can be set to gbk_chinese_ci or gbk_bin.
- If character_set_server is set to utf8, collation_server can be set to utf8_unicode_ci or utf8_bin.
- If character_set_server is set to utf8mb4, collation_server can be set to utf8mb4_unicode_ci or utf8mb4_bin.
sql_audit
OFF
OFF or ON
Whether to enable or disable SQL audit.
ddm_instance_type
-
SINGLE,MASTER,SLAV
SINGLE: indicates that the DDM instance is a single instance.
SLAVE: indicates that the DDM instance is the standby instance for across-region DR.
MASTER: indicates that the DDM instance is the primary instance for across-region DR.
transaction_policy
XA
XA, FREE, NO_DTX
XA: XA transaction that attempts to ensure atomicity and visibility.
FREE: Best-effort commit transaction that allows data to be written to multiple shards, without impacting performance. This setting does not ensure atomicity.
NO_DTX: With this setting, single-shard transactions are performed.
By default, DDM only allows you to modify the preceding instance parameters. If you need to modify other parameters for some special scenarios, such as data migration, contact customer service.
Parameter configuration examples:Figure 2 Result if bind_table is not usedFigure 3 Result if bind_table is used - Click Save in the upper left corner and then Yes in the displayed dialog box.
Figure 4 Confirming the parameter modification
NOTE:
- Modifying DDM parameters may affect access to the instance. Exercise caution when performing this operation.
- It takes 20s to 60s to have the modifications to take effect.
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