FAQ

Problem categories

Common problems fall into these categories:

• Billing issues

• Performance and specification issues

• Precheck issues

  For precheck details, see Precheck items and methods to fix precheck failures.

• Database connection issues

• Data synchronization issues

• Data migration issues

• Data Subscription Issues

• Data validation issues

• Other issues

Billing issues

How is DTS billed?

DTS supports subscription and pay-as-you-go billing. Billing overview.

How do I view DTS bills?

To view DTS bills, see View bills.

Am I charged for paused instances?

• You are not charged for paused data migration instances.

• During the suspension of a data synchronization instance, charges continue to apply regardless of whether the source or destination database is accessible. This is because, during this period, DTS only pauses writing data to the destination database, but still consumes resources such as CPU and memory to maintain persistent connections to the database and pull logs from the source database, so that the instance can resume quickly after being restarted.

Why is data synchronization more expensive than data migration?

Data synchronization supports more advanced features, such as modifying synchronization objects online and two-way synchronization between MySQL databases. It also uses internal network transmission for lower latency.

What are the impacts of overdue payments?

See Expiration or overdue payments.

How do I release a subscription task in advance?

To release a subscription instance, see Unsubscribe from a subscription instance.

Can I switch the billing method of a task from subscription to pay-as-you-go?

Yes. Switch between billing methods.

Can I switch the billing method of a task from pay-as-you-go to subscription?

Why did my DTS task suddenly start incurring fees?

The free trial period for the instance may have expired. DTS offers free trials for tasks where the destination is an Alibaba Cloud-developed database engine. After the trial expires, standard billing applies.

Why am I still being charged for a released task?

Pay-as-you-go DTS bills are generated daily. You are charged for the day on which you release the task, because you used the DTS service on that day.

How does pay-as-you-go billing work?

You are charged for a pay-as-you-go task only when the task is running. This period includes the time when an Incremental Data Synchronization task is paused, but does not include the time when an Incremental Data Migration task is paused. Billing method.

Does DTS charge for traffic?

Some DTS tasks incur fees for public network and data traffic, regardless of the regions of the source and destination databases. A migration task incurs public network traffic fees if the Access Method for the destination database is set to Public IP Address. A full validation task in Full field validation by row sampling mode incurs data traffic fees based on the amount of validated data. Billable items.

Does DTS support savings plans?

No, it does not. You can use Serverless instances to reduce costs. What is a DTS Serverless instance?.

Performance and specification issues

What are the differences between instance types?

See Data migration link specifications and Data synchronization link specifications.

Can I upgrade an instance type?

Can I downgrade an instance type?

Can I downgrade the instance type of a DTS task?

DTS tasks that meet the requirements support downgrading (downgrading the link specifications). For more information, see Downgrade an instance class

Can I downgrade a DTS task to a specification lower than medium?

Not supported.

How long does it take to synchronize or migrate data?

The time required for a DTS task cannot be accurately estimated. Performance depends on many factors, such as the load on the DTS, source, and destination database instances, data volume, the existence of incremental tasks, and network conditions. If you have high performance requirements, select an instance type with a higher performance limit. See Data migration link specifications and Data synchronization link specifications.

How do I view the performance information of a data migration or data synchronization task?

See View the status and performance of an incremental migration link or View the status and performance of a synchronization link.

Why can't I find a specific DTS instance in the console?

Precheck issues

Why does the Redis eviction policy check item generate an alert?

If the data eviction policy (maxmemory-policy) of the destination database is set to a value other than noeviction, the destination data may become inconsistent with the source. Introduction to Redis data eviction policies.

What do I do if a binary logging-related precheck item fails during incremental data migration?

Check whether the binary logs of the source database are functioning correctly. Source database binary logging check.

Database connection issues

What do I do if the connection to the source database fails?

Check whether the source database information and settings are correct. Source database connectivity check.

What do I do if the connection to the destination database fails?

Check whether the destination database information and settings are correct. Destination database connectivity check.

What do I do if the source or destination instance is in a region that is not supported by DTS and I want to perform data migration and synchronization?

• For a data migration task, you can request a public endpoint for the database instance, such as an RDS MySQL instance, and use the Public IP Address connection type. This requires you to select a DTS-supported region for the instance and add the CIDR blocks of the DTS servers in that region to the instance's whitelist. Add the CIDR blocks of DTS servers to the IP whitelist.

• DTS does not support data synchronization in these regions because it does not support the Public IP Address connection type for database instances.

How long does it take for DTS to detect a domain name switch for a source or destination instance?

DTS detects the domain name binding switch within 10 minutes and automatically switches the DTS task to the new IP address bound to the domain name. During the domain name switch, make sure that the binary logging replication relationship between the old and new instances is maintained for more than 10 minutes.

Data synchronization issues

Which database instances does DTS support for synchronization?

DTS supports synchronization between various data sources, including RDBMS, NoSQL, and OLAP databases. Overview of data synchronization solutions.

What is the difference between data migration and data synchronization?

The following table compares data migration and data synchronization.

How does data synchronization work?

Service architecture and features.

How is synchronization latency calculated?

Synchronization latency is the time difference in milliseconds between the timestamp of the latest data synchronized to the destination database and the current timestamp of the source database.

Can I modify the synchronization objects of a data synchronization task?

Yes. Add a synchronization object and Remove a synchronization object.

Can I add a new table to a data synchronization task?

Yes. Add a synchronization object.

How do I modify the synchronization objects, such as tables and fields, of a running synchronization task?

You can modify synchronization objects after full synchronization completes and incremental synchronization begins. Add a synchronization object and Remove a synchronization object.

If I pause a synchronization task and then restart it after a period of time, will this cause data inconsistency?

If the source database changes while the synchronization task is paused, data inconsistency between the source and destination databases may occur. After you restart the synchronization task and the incremental data is synchronized to the destination database, the data in the destination database becomes consistent with the data in the source database.

If I delete data from the source database of an incremental synchronization task, will the synchronized data in the destination database be deleted?

If the DML operations to be synchronized for the incremental synchronization task do not include delete, the data in the destination database is not deleted. Otherwise, the synchronized data in the destination database is deleted.

Will the data in the destination Redis instance be overwritten during synchronization between Redis instances?

Yes, data with the same key is overwritten. DTS checks the destination during the precheck phase. If the destination is not empty, an error is reported.

Can a synchronization task filter some fields or data?

Yes. You can use the mapping feature to filter columns and specify SQL WHERE conditions to filter data. Synchronize or migrate some columns and Filter data using SQL conditions.

Can a synchronization task be converted to a migration task?

No. Tasks of different types cannot be converted to each other.

Can I synchronize only data without synchronizing the schema?

Yes, you can. When you configure the synchronization task, do not select Schema Synchronization.

What are the possible causes of data inconsistency between the source and destination of a data synchronization instance?

Can I change the name of the source database in the destination database for a data synchronization task?

Yes. Set the name of a synchronization object in the destination instance.

Is real-time synchronization of DML or DDL operations supported?

Yes. Data synchronization for relational data supports DML (INSERT, UPDATE, and DELETE) and DDL (CREATE, DROP, ALTER, RENAME, and TRUNCATE) operations.

Can a read-only instance be used as the source instance for a synchronization task?

Does DTS support data synchronization for sharded databases and tables?

Yes, you can. For example, you can merge multiple sharded tables by synchronizing them from MySQL and PolarDB for MySQL to AnalyticDB for MySQL.

Why is the data volume of the destination instance smaller than that of the source instance after a synchronization task is complete?

If data was filtered during synchronization, or if there are many table fragments in the source instance, the data volume of the destination instance may be smaller than that of the source instance after the synchronization is complete.

Does a cross-account data synchronization task support two-way synchronization?

Yes, but currently, only two-way synchronization tasks between ApsaraDB RDS for MySQL instances, between PolarDB for MySQL clusters, between Tair (Enterprise Edition) instances, between ApsaraDB for MongoDB (ReplicaSet) instances, or between ApsaraDB for MongoDB (sharded cluster) instances support cross-account two-way synchronization.

Does the reverse synchronization of a two-way synchronization instance support DDL synchronization?

Not supported. Only forward synchronization tasks (i.e., synchronizing from the source database to the destination database) support DDL synchronization. Reverse synchronization tasks (i.e., synchronizing from the destination database to the source database) do not support DDL synchronization, and DDL operations are automatically filtered out.

Do I need to manually configure a reverse synchronization task?

Yes. Wait for the forward synchronization task to complete initialization (until the Status is Running). Then, locate the reverse synchronization task and click Configure Task.

Does DTS support cross-border two-way synchronization tasks?

No, it does not.

Why is a record not added to the other database when it is added to one database in a two-way synchronization task?

This issue may occur because a reverse task was not configured.

Why does the incremental synchronization task never reach 100%?

An incremental synchronization task continuously synchronizes changes from the source to the destination in real time and does not end on its own. This means there is no 100% completion state. If you no longer need real-time synchronization, you can end the task in the DTS console.

Why can't an incremental synchronization task synchronize data?

If a DTS instance is configured for only incremental synchronization, DTS synchronizes only the incremental data generated after the task starts. This means that data generated before the task starts is not synchronized to the destination database. To ensure data consistency, we recommend that you select Incremental Data Synchronization, Schema Synchronization, and Full Data Synchronization when you configure the task.

Does synchronizing full data from an RDS database affect the performance of the source RDS instance?

Why does a synchronization instance with a PolarDB-X 1.0 source not display latency?

Latency information is not displayed for instances with a PolarDB-X 1.0 source. This is because the instance runs as a distributed task, and metrics monitored by DTS exist only in subtasks. To view the latency information, click the instance ID and go to the Subtask Details section on the Task Management page.

Why does a multi-table merge task report the DTS-071001 error?

This error may occur because you performed online DDL operations on the source database while the multi-table merge task was running. These operations modified the table schema of the source database, but you did not make the corresponding changes in the destination database.

What do I do if adding a whitelist fails when I configure a task in the legacy console?

You can use the new console to configure the task.

What do I do if a data synchronization task fails because a DDL operation was performed on the source database during the process?

Based on the DDL operation that was performed on the source database, manually execute the DDL operation on the destination database and restart the task. During data synchronization, do not use tools such as pt-online-schema-change to perform online DDL operations on the synchronization objects of the source database. Otherwise, the synchronization fails. If no data other than DTS data is written to the destination database, you can use Data Management (DMS) to perform online DDL operations, or you can modify the synchronization objects to remove the affected tables. Remove a synchronization object.

What do I do if a data synchronization task fails because a DDL operation was performed on the destination database during the process?

Can a synchronization task be restored after it is released? Can reconfiguring the task ensure data consistency?

A synchronization task cannot be restored after it is released. If you reconfigure the task without selecting Full Data Synchronization, any data added between the release of the original task and the start of the new task will not be synchronized to the destination database, and data consistency cannot be guaranteed. If data accuracy is critical for your business, you can delete the data in the destination database, reconfigure the synchronization task, and select both Schema Synchronization and Full Data Synchronization in the Task Stages. Incremental Data Synchronization is selected by default.

What do I do if a DTS full synchronization task shows no progress for a long time?

If the table to be synchronized has no primary key, full synchronization will be very slow. We recommend that you add a primary key to the table to be synchronized in the source database before you start the synchronization.

When synchronizing data between tables with the same name, can I configure it so that data from the source table is transferred only if it does not exist in the destination table?

Yes. When you configure the task, you can set Processing Mode of Conflicting Tables to Ignore Errors and Proceed. If the table schemas are consistent, and a record from the source database has a primary key value that already exists in the destination database, that record will not be synchronized during a full synchronization.

How do I configure a cross-account synchronization task?

What do I do if I cannot select a DMS LogicDB instance?

Make sure that the region of the instance is correct. If you still cannot select the instance, there may be only one instance. You can continue to configure other parameters.

Does a synchronization task with a SQL Server source support synchronizing functions?

No, it does not. If the synchronization object granularity is set to table, other objects such as views, triggers, and stored procedures will not be synchronized to the destination database.

What do I do if a data synchronization task reports an error?

You can find a solution in Common errors based on the error message.

How do I enable hot spot merge for a synchronization task?

See Modify parameter values to change the value of trans.hot.merge.enable to true.

How do I perform synchronization when the source database has triggers?

When the synchronization object is the entire database and a trigger updates a table in the database, data inconsistency may occur. Configure a synchronization or migration job when the source database has triggers.

Does DTS support synchronizing the sys database and system databases?

No, it does not.

Does DTS support synchronizing the admin and local databases of MongoDB?

No, it does not. DTS does not support using the admin and local databases of MongoDB as the source or destination.

When can the reverse task of a two-way synchronization task be configured?

The reverse task of a two-way synchronization task can be configured only after the forward incremental task has no latency.

When PolarDB-X 1.0 is the source, does the source PolarDB-X 1.0 of a synchronization task support node scaling?

No, it does not. If the source PolarDB-X 1.0 undergoes node scaling, you need to reconfigure the task.

Can the data synchronized to Kafka by DTS be guaranteed to be unique?

No, it cannot. Because data written to Kafka is appended, there may be duplicate data when the DTS task is restarted or when it repeatedly pulls logs from the source. DTS ensures data idempotence, which means that data is arranged in order, and the latest value of duplicate data will be placed at the end.

Does DTS support data synchronization from RDS for MySQL to AnalyticDB for MySQL?

Yes. Synchronize data from RDS for MySQL to AnalyticDB for MySQL 3.0.

Why does a synchronization task between Redis instances not show full synchronization?

Synchronization between Redis instances includes both full and incremental data synchronization. These two methods are collectively displayed as Incremental Data Synchronization.

Can full synchronization be skipped?

Yes, it can. After you skip full synchronization, incremental synchronization will continue, but errors may occur. We recommend that you do not skip full synchronization.

Can I schedule automatic synchronization?

No, DTS does not currently support scheduling the start of data synchronization tasks.

Will table fragmentation be synchronized during the process?

No, it will not.

What should I be aware of when synchronizing from MySQL 8.0 to MySQL 5.6?

You need to create a database in MySQL 5.6 before you perform the synchronization operation. We recommend that the source and destination database versions be consistent, or that you synchronize from a lower version to a higher version to ensure compatibility. If you synchronize from a higher version to a lower version, database compatibility issues may occur.

Can accounts in the source database be synchronized to the destination database?

Currently, only synchronization tasks between ApsaraDB RDS for MySQL instances support synchronizing accounts. Other synchronization tasks do not.

Can I configure a cross-account two-way synchronization task?

Yes, but currently, only two-way synchronization tasks between ApsaraDB RDS for MySQL instances, between PolarDB for MySQL clusters, between Tair (Enterprise Edition) instances, between ApsaraDB for MongoDB (ReplicaSet) instances, or between ApsaraDB for MongoDB (sharded cluster) instances support cross-account two-way synchronization.

How do I configure parameters when Message Queue for Apache Kafka is the destination?

Configure parameters as needed. Configure parameters for a Message Queue for Apache Kafka instance.

How do I resolve the ERR invalid DB index error when I use DTS to synchronize or migrate Redis data?

Cause: The ERR invalid DB index error occurs when the destination database executes the SELECT DB operation. This is usually because the number of databases in the destination database is insufficient. If the destination database uses a proxy, check whether the proxy can lift the limit on the number of databases.

Solution: Modify the databases configuration of the destination database. Increase the number to match the source database, and then restart the DTS task. You can run the following command to query the databases configuration of the destination database:

CONFIG GET databases;

How do I resolve the IDENTIFIER CLUSTERED error when I synchronize or migrate SQL Server data to AnalyticDB for PostgreSQL?

Cause: When you synchronize or migrate SQL Server data to AnalyticDB for PostgreSQL, the task fails because the CREATE CLUSTERED INDEX command is not supported.

Solution: After you confirm that there are no other DDL commands during the latency period, modify the instance parameter sink.ignore.failed.ddl to true to filter out all DDL executions. After the incremental synchronization or migration offset advances, change sink.ignore.failed.ddl back to false.

In a Redis synchronization or migration task, does extending the expiration time of a key in the destination database have any practical effect?

To prevent keys from expiring during full data synchronization, you can extend the key expiration time in the destination database. For DTS tasks that involve incremental synchronization or migration, if a key in the source database expires and is deleted, the corresponding key in the destination database is also released.

After setting an extended expiration time for a key in the destination database, if the key in the source database expires, will the key in the destination database be released immediately?

A key in the destination database is not necessarily released immediately upon expiration. It is released immediately only when the corresponding key in the source database expires and is cleared.

For example, if a key in the source database is set to expire in 5 seconds, but the key's expiration time in the destination database is 30 seconds, the key in the destination database is deleted when the source key expires. When the key in the source database expires, the system adds a delete operation to the Append-Only File (AOF). This request is then synchronized to the destination database and executed.

How do I correct an incorrectly configured destination table name mapping?

On the DTS task configuration page, expand the destination database in the Selected Objects section, find the table with the incorrect mapping, and click the Edit button on the right. In the dialog box that appears, change the destination table name to the correct name and save the change.

How do I backfill historical data after adding a new column?

DTS does not automatically backfill historical data for newly added columns. This rule applies to all destination database types, not just SelectDB. To backfill historical data, perform the following steps:

1. Manually add the new field to the destination table.

2. In the DTS console, modify the synchronization objects to remove the table from the synchronization list.

3. Run TRUNCATE to clear the data from the destination table to ensure data consistency.

4. Re-add the table to the synchronization objects. This triggers both full and incremental data synchronization to migrate the historical data to the destination.

Data migration issues

Will the data in the source database still exist after a data migration task is executed?

DTS performs data migration and synchronization by copying data from a source database to a destination database without affecting the source.

Which database instances does DTS support for migration?

DTS supports migration between various data sources, including RDBMS, NoSQL, and OLAP databases. Overview of data migration solutions

How does data migration work?

Service architecture and features.

Can I modify the migration objects of a data migration task?

No, you cannot.

Can I add a new table to a data migration task?

No, you cannot.

How do I modify the migration objects, such as tables and fields, of a running migration task?

Migration tasks do not support modifying migration objects.

If I pause a migration task and then restart it after a period of time, will this cause data inconsistency?

If the source database changes while the migration task is paused, data inconsistency between the source and destination databases may occur. After you restart the migration task and the incremental data is migrated to the destination database, the data in the destination database becomes consistent with the data in the source database.

Can a migration task be converted to a synchronization task?

No. Tasks of different types cannot be converted to each other.

Can I migrate only data without migrating the schema?

Yes, you can. When you configure the migration task, do not select Schema Migration.

What are the possible causes of data inconsistency between the source and destination of a data migration instance?

Can I change the name of the source database in the destination database for a data migration task?

Yes. Database, table, and column mapping.

Is data migration within the same instance supported?

Yes. Data synchronization or migration between different database names.

Is real-time migration of DML or DDL operations supported?

Yes, it is. The supported DML operations for data between relational databases are INSERT, UPDATE, and DELETE. The supported DDL operations are CREATE, DROP, ALTER, RENAME, and TRUNCATE.

Can a read-only instance be used as the source instance for a migration task?

Does DTS support data migration for sharded databases and tables?

Yes, it does. For example, you can migrate sharded databases and tables in MySQL and PolarDB for MySQL to AnalyticDB for MySQL to merge multiple tables.

Can a migration task filter some fields or data?

Yes. You can use the mapping feature to filter columns and specify SQL WHERE conditions to filter data. Synchronize or migrate some columns and Filter data to be migrated.

Why is the data volume of the destination instance smaller than that of the source instance after a migration task is complete?

If data was filtered during migration, or if there are many table fragments in the source instance, the data volume of the destination instance may be smaller than that of the source instance after the migration is complete.

Why is the value of "Completed" greater than the total in a migration task?

The displayed total is an estimated value. After the migration task is complete, the total will be adjusted to the accurate value.

What is the purpose of the increment_trx table added to the destination database during data migration?

The increment_trx table is an offset table that DTS incremental migration creates in the destination instance. It is mainly used to record the offset of incremental migration and solve the problem of resuming from a breakpoint after an abnormal task restart. Do not delete it during the migration process. Otherwise, the migration will fail.

Does a data migration task support resuming from a breakpoint during the full migration phase?

Yes, it does. If you pause a task during the full migration phase and then restart it, the task will continue from where it left off, without starting over.

How do I migrate a non-Alibaba Cloud instance to Alibaba Cloud?

Migrate data from a third-party cloud to Alibaba Cloud.

How do I migrate an on-premises Oracle database to PolarDB?

Migrate data from a self-managed Oracle database to a PolarDB for PostgreSQL (Compatible with Oracle) database.

Can a data migration task that has not completed the full migration phase be paused?

Yes, it can.

How do I migrate some data from RDS for MySQL to a self-managed MySQL database?

When you configure the migration task, you can select the objects to be migrated in the Source Objects section or filter them in the Selected Objects section as needed. The migration operations between MySQL databases are similar. Migrate data from a self-managed MySQL database to an ApsaraDB RDS for MySQL instance.

How do I migrate RDS instances under the same Alibaba Cloud account?

DTS supports migration and synchronization between RDS instances. See the relevant configuration documents in Overview of data migration solutions.

What do I do if an IOPS alert is triggered for the source database after a migration task starts, and how do I ensure the stability of the source database business?

Why can't a data migration task select a database named "test"?

DTS data migration does not support migrating system databases. You must select a business-created database for migration.

Why does a migration instance with a PolarDB-X 1.0 source not display latency?

Latency information is not displayed for instances with a PolarDB-X 1.0 source. This is because the instance runs as a distributed task, and metrics monitored by DTS exist only in subtasks. To view the latency information, click the instance ID and go to the Subtask Details section on the Task Management page.

Why can't DTS migrate a MongoDB database?

This may be because the database to be migrated is "local" or "admin". DTS does not support using the admin and local databases of MongoDB as the source or destination.

Why does a multi-table merge task report the DTS-071001 error?

This error may occur because you performed online DDL operations on the source database while the multi-table merge task was running. These operations modified the table schema of the source database, but you did not make the corresponding changes in the destination database.

What do I do if adding a whitelist fails when I configure a task in the legacy console?

You can use the new console to configure the task.

What do I do if a data migration task fails because a DDL operation was performed on the source database during the process?

Based on the DDL content that was executed on the source database, manually execute the DDL operation on the destination and restart the task. During data migration, do not use tools such as pt-online-schema-change to perform online DDL operations on the migration objects of the source database. Otherwise, the migration will fail. If no data other than DTS data is written to the destination database, you can use Data Management (DMS) to perform online DDL operations.

What do I do if a data migration task fails because a DDL operation was performed on the destination database during the process?

If a database or table in the destination database is deleted during incremental migration and causes the task to become abnormal, you can reconfigure the task and not select the database or table that caused the failure as a migration object.

Can a migration task be restored after it is released? Can reconfiguring the task ensure data consistency?

A migration task cannot be restored after it is released. If you reconfigure the task without selecting Full Data Migration, data added after the task is released will not be migrated to the destination database, and data consistency cannot be guaranteed. If high data accuracy is required, you can delete the data in the destination database, reconfigure the migration task, and select Schema Migration, Incremental Data Migration, and Full Data Migration in the Task Stages.

What do I do if a DTS full migration task shows no progress for a long time?

If the table to be migrated has no primary key, full migration will be very slow. We recommend that you add a primary key to the table to be migrated in the source database before you start the migration.

When migrating data between tables with the same name, can I configure it so that data from the source table is transferred only if it does not exist in the destination table?

Yes, you can. When you configure the task, you can set Processing Mode of Conflicting Tables to Ignore Errors and Proceed. If the table schemas are consistent, source records with primary keys that already exist in the destination database will not be migrated during the full migration.

How do I configure a cross-account migration task?

How does a data migration task connect to an on-premises database?

Set the Access Method for the on-premises database to Public IP Address to configure the migration task. Migrate data from a self-managed MySQL database to an ApsaraDB RDS for MySQL instance.

What do I do if a data migration fails with the DTS-31008 error?

Based on the error message, you can click View Cause or refer to Common errors.

What do I do if the network is disconnected when connecting to a self-managed database through a leased line?

Check whether the DTS-related IP address whitelist is correctly configured for the leased line. For the list of IP addresses to be added to the whitelist, see Add the CIDR blocks of DTS servers to the IP whitelist.

Does a migration task with a SQL Server source support migrating functions?

No, it does not. If the migration object granularity is set to table, other objects such as views, triggers, and stored procedures will not be migrated to the destination database.

What do I do if a DTS full migration is slow?

The data migration may take some time to complete. You can view the migration progress in the Full Data Migration module of the task details on the Task Management page.

What do I do if the task reports an internal error?

You can use DingTalk (Download the DingTalk client) to join the DTS Customer Communication DingTalk group (Group ID: 116655009709) for assistance.

What do I do if schema migration reports an error?

Click the instance ID to go to the task details page. View the error message in the schema migration module on the Task Management page and resolve the error accordingly. For solutions to common errors, see Common errors.

Are schema migration and full migration free of charge?

This is free. Billing Items.

Will the zset data in the destination be overwritten during a data migration task between Redis instances?

Yes, the zset in the destination will be overwritten. If a key that is the same as in the source already exists in the destination, DTS will first delete the zset of the corresponding key in the destination, and then zadd each object in the source zset collection to the destination.

What is the impact of full migration on the source database?

The process of DTS full migration is to first segment the data, and then read and write the data within the segments. For the source database, the IOPS of the source database will increase during the data segmentation process. During the process of reading data within the segments, the IOPS, CachePool, and outbound bandwidth of the source database will be affected to some extent. Based on DTS's practical experience, these impacts are negligible.

When PolarDB-X 1.0 is the source, does the source PolarDB-X 1.0 of a migration task support node scaling?

No, it does not. If the source PolarDB-X 1.0 undergoes node scaling, you need to reconfigure the task.

Can the data migrated to Kafka by DTS be guaranteed to be unique?

No, it cannot. Because data written to Kafka is appended, there may be duplicate data when the DTS task is restarted or when it repeatedly pulls logs from the source. DTS ensures data idempotence, which means that data is arranged in order, and the latest value of duplicate data will be placed at the end.

If I configure a full migration task first, and then an incremental data migration task, will data inconsistency occur?

Yes, data inconsistency may occur. When an incremental data migration task is configured separately, the task starts migrating data only after it is started. Incremental data that is generated in the source instance before the incremental migration task starts will not be synchronized to the destination instance. To perform a zero-downtime migration, we recommend that you select schema migration, full data migration, and incremental data migration as the migration types when you configure the task.

Do I need to select schema migration when I configure an incremental migration task?

Schema migration is the process of migrating the definitions of migration objects to the destination instance before data migration begins, such as migrating the table definition of table A to the destination instance. To perform incremental migration, we recommend that you select schema migration, full data migration, and incremental data migration to ensure data consistency.

Why is the storage space used by RDS larger than the source database during migration from a self-managed database to RDS?

Because DTS performs a logical migration, it encapsulates the data to be migrated into SQL and migrates it to the destination RDS instance. At this time, binary log data will be generated in the destination RDS instance, so the storage space used by RDS during the migration process may be larger than the source database.

Does DTS support migrating MongoDB in a VPC?

Yes, it does. DTS currently supports using ApsaraDB for MongoDB in a VPC as the source database for migration.

What happens to the migrated data if the source database changes during data migration?

If the migration task is configured with schema migration, full migration, and incremental migration, any data changes that occur in the source database during the migration will be migrated to the destination database by DTS.

Will releasing a completed migration task affect the use of the migrated database?

No. You can safely release a migration task only after it is complete, which is when its Status is Completed.

Does DTS support incremental migration for MongoDB?

Yes. See the relevant configuration examples in Overview of data migration solutions.

What is the difference between using an RDS instance and a self-managed database instance with a public IP address as the source for a migration task?

If you select an RDS instance when you configure a migration task, the DTS migration task can adapt to changes such as DNS modifications and network type switches of the RDS instance, which effectively ensures link reliability.

Does DTS support migrating a self-managed database on an ECS instance in a VPC to an RDS instance?

Does DTS lock tables during migration? Does it affect the source database?

DTS does not lock tables on the source database during full data migration and incremental data migration. During full data migration and incremental data migration, the data tables of the migration source can be accessed for reading and writing normally.

When DTS performs RDS migration, does it get data from the primary or secondary RDS database?

When DTS performs data migration, it pulls data from the primary RDS database.

Can I schedule automatic migration?

No, DTS does not currently support scheduling the start of data migration tasks.

Does DTS support data migration for RDS instances in VPC mode?

Yes, you can specify the RDS instance ID when you configure a migration task.

When DTS performs migration or synchronization for the same account or across accounts, does it use the internal network or the public network for ECS and RDS instances? Are there traffic fees?

Will the data in the source database be deleted after migration using DTS?

No, it will not. When DTS performs data migration, it copies the data from the source database to the destination database and does not affect the data in the source database.

When DTS performs data migration between RDS instances, can I specify the name of the destination database?

Yes. When you perform data migration between RDS instances, use the database name mapping feature to specify the destination database name. Data synchronization or migration between different database names.

What do I do if the source of a DTS migration task cannot connect to an ECS instance?

The ECS instance may not have a public IP address exposed. Bind an EIP to the ECS instance and try again. Elastic IP Address.

Why does a migration task between Redis instances not show full migration?

You can migrate data between Redis instances using Incremental Data Migration, which combines full data migration and incremental data migration.

Can full migration be skipped?

Yes, it can. After you skip full migration, incremental migration will continue, but errors may occur. We recommend that you do not skip full migration.

Does a cluster edition of Redis support connecting to DTS with a public IP address?

No, it does not. Currently, only a standalone edition of Redis supports connecting to a DTS migration instance with a public IP address.

What should I be aware of when migrating from MySQL 8.0 to MySQL 5.6?

You need to create a database in MySQL 5.6 before you perform the migration operation. We recommend that the source and destination database versions be consistent, or that you migrate from a lower version to a higher version to ensure compatibility. If you migrate from a higher version to a lower version, database compatibility issues may occur.

Can accounts in the source database be migrated to the destination database?

Currently, only migration tasks between ApsaraDB RDS for MySQL instances support migrating accounts. Other migration tasks do not.

How do I configure parameters when Message Queue for Apache Kafka is the destination?

Configure parameters as needed. Configure parameters for a Message Queue for Apache Kafka instance.

How do I perform scheduled full migration?

You can use the scheduling policy of the data integration feature to periodically migrate schema and historical data from the source to the destination. Configure a data integration task between ApsaraDB RDS for MySQL instances.

Is it supported to migrate a self-managed SQL Server on an ECS instance to an on-premises self-managed SQL Server?

Yes. The on-premises self-managed SQL Server needs to be connected to Alibaba Cloud. Overview of preparations.

Is it supported to migrate PostgreSQL databases from other clouds?

Yes, data migration through DTS is supported when a PostgreSQL database from another cloud allows DTS to access it through the public network.

Is it supported to migrate data from MySQL to Mycat?

Yes, it is. You can connect Mycat to Alibaba Cloud as a self-managed MySQL database and then use DTS for data migration.

How many data migration instances can I try for free?

You can try one migration instance for free for three months. Alibaba Cloud Free Trial.

Does data migration support incremental migration of DDL operations?

Yes, it is supported in some migration scenarios. Notes and limits for migration tasks.

Data Subscription Issues

How does data subscription work?

Service Architecture and Principles.

What data can a change tracking instance track? What information can be obtained?

You can track the creation, deletion, and modification of the schema of the destination tracking object, along with updates (INSERT, DELETE, and UPDATE operations) to the data of the tracked object.

Will the consumer group be deleted after a change tracking task expires?

After a DTS change tracking task expires, the data consumer group is retained for seven days. If the instance is not renewed within seven days after it expires, it will be released, and the corresponding consumer group will also be deleted.

Can a read-only instance be used as the source instance for a tracking task?

How do I consume tracked data?

Consuming subscription data.

Why does the date data format change after data is transferred using the change tracking feature?

The default date data storage format for DTS is YYYY:MM:DD. YYYY-MM-DD is the displayed format, but the actual storage format is YYYY:MM:DD. Therefore, regardless of the format of the transferred data, it will eventually be converted to the default format.

How do I troubleshoot a tracking task?

Troubleshoot a tracking task.

What do I do if the SDK suddenly pauses and cannot track data while downloading data normally?

Check whether the ackAsConsumed interface is called in the SDK code to report the consumer offset. If ackAsConsumed is not called to report the offset, the data in the Record cache space set inside the SDK will not be deleted. When the cache is fully occupied, new data cannot be pulled, which will cause the SDK to pause and be unable to track data.

What do I do if the SDK cannot successfully track data after being rerun?

Before you start the SDK, modify the consumer offset to make it within the data range. Save and query consumer offsets.

How does a client specify a point in time for data consumption?

When you consume tracked data, you can fill in the initCheckpoint parameter to specify a point in time. Use SDK sample code to consume tracked data.

How do I reset the offset if a DTS tracking task has a backlog?

1. According to the usage mode of the SDK client, open the corresponding code file, such as DTSConsumerAssignDemo.java or DTSConsumerSubscribeDemo.java.

   Note

   Use SDK sample code to consume tracked data.

2. In the Data Range column of the tracking task list, you can view the modifiable offset range for the destination tracking instance.

3. Select a new consumer offset as needed and convert it to a UNIX timestamp.

4. Use the converted new consumer offset to replace the old consumer offset (initCheckpoint parameter) in the code file.

5. Rerun the client.

What do I do if the client cannot connect using the VPC address of the tracking task?

The machine where the client is located may not be in the VPC that was specified when the tracking task was configured (for example, the client VPC was changed). You need to reconfigure the task.

Why is the consumer offset in the console larger than the maximum value of the data range?

This is because the update frequency of the data range of the tracking channel is 1 minute, while the update frequency of the consumer offset is 10 seconds. So if you consume in real time, the value of the consumer offset may be larger than the maximum value of the tracking channel data range.

How does DTS ensure that the data tracked by the SDK is a complete transaction?

DTS searches for the complete transaction that corresponds to the provided consumer offset. The server-side distributes data downstream starting from the BEGIN statement of the entire transaction, so the complete transaction content can be received.

How do I confirm whether data is being consumed normally?

If data is being consumed normally, the consumer offset in the Data Transmission Service console will move forward normally.

What does usePublicIp=true mean in the change tracking SDK?

In the change tracking SDK configuration, usePublicIp=true means that the SDK accesses the DTS tracking channel through the public network.

Will the business be affected when the primary RDS database of a change tracking task is switched or restarted?

When a primary/secondary switchover or restart occurs for an ApsaraDB RDS for MySQL, ApsaraDB RDS for PostgreSQL, PolarDB for MySQL, PolarDB for PostgreSQL, or PolarDB-X 1.0 (storage type is RDS for MySQL) instance, DTS will adaptively switch, and the business will not be affected.

Does RDS provide a tool for automatic binary log download to a local server?

The change tracking feature of DTS supports real-time tracking of RDS binary logs. You can activate the DTS change tracking service and use the DTS SDK to track RDS binary log data and synchronize it to a local server in real time.

Does the real-time incremental data of change tracking refer only to new data, or does it include modified data?

The incremental data that can be tracked by DTS change tracking includes all additions, deletions, modifications, and schema changes (DDL).

Why does the SDK receive duplicate data after restarting if a record is not ACKed by the consumer end of a change tracking task?

When a message is not ACKed by the SDK, the server-side will finish pushing all messages in the buffer. After the push is complete, the SDK can no longer receive messages. At this time, the consumer offset saved by the server-side is the offset of the last message before the un-ACKed one. When the SDK restarts, to ensure that no messages are lost, the server-side will re-push data from the offset corresponding to the message before the un-ACKed one. Therefore, the SDK will receive some duplicate messages.

How often is the change tracking consumer offset updated, and why does the SDK sometimes receive duplicate data when it is restarted?

After the change tracking SDK consumes each message, it must call ackAsConsumed to reply with an ACK to the server-side. After receiving the ACK, the server-side updates the consumer offset in memory and then persists the consumer offset every 10 seconds. If the SDK is restarted before the latest ACK is persisted, the server-side will start pushing messages from the last persisted consumer offset to ensure that no messages are lost. In this case, the SDK will receive duplicate messages.

Can one change tracking instance track multiple RDS instances?

No, it cannot. Currently, one change tracking instance can track only one RDS instance.

Will data inconsistency occur in a change tracking instance?

No, it will not. A change tracking task only obtains the changes from the source database and does not involve data inconsistency. If the data consumed by the client is inconsistent with what you expect, you must troubleshoot it yourself.

What to do when UserRecordGenerator appears while consuming subscription data?

When you consume tracked data, if you see a message such as UserRecordGenerator: haven't receive records from generator for 5s, you need to check whether the consumer offset is within the offset range of the incremental data ingestion module and ensure that the consumer end is running normally.

Can multiple partitions be created for one topic?

No, they cannot. To ensure the global order of messages, each tracking topic in DTS has only one partition, which is fixedly assigned to partition 0.

Does the change tracking SDK support Go?

Supported. For sample code, see the dts-subscribe-demo repository.

Does the change tracking SDK support Python?

Yes, there is. For sample code, see dts-subscribe-demo.

Does flink-dts-connector support multi-threaded concurrent consumption of tracked data?

No, it does not.

Can I configure both a change tracking task and a data synchronization task for the same RDS instance?

Yes. The two tasks do not interfere with each other. A change tracking task and a data synchronization task are two independent task types that can coexist on the same RDS instance without mutual interference.

Data validation issues

Other issues

What is the impact of modifying data in the destination database while a data synchronization or migration task is running?

• Modifying data in the destination database may cause the DTS task to fail. During data migration or synchronization, if you perform operations on the objects to be migrated or synchronized in the destination database, it may cause primary key conflicts, no update records, or other situations, which will eventually cause the DTS task to fail. However, you can perform operations that will not interrupt the DTS task, such as creating a table in the destination instance and writing to it. Because this table is not in the migration or synchronization object table, it will not cause the DTS task to fail.

• Because DTS reads the source instance database information and migrates or synchronizes its full data, schema data, and incremental data to the destination instance, data that is modified in the destination database during the task may be overwritten by the data migrated or synchronized from the source database.

Can data be written to both the source and destination databases at the same time while a data synchronization or migration task is running?

Yes, but if data is written to the destination database from other data sources besides DTS while the DTS instance is running, it may cause the destination database data or the DTS instance to become abnormal.

What happens if I change the password of the source or destination database while a DTS instance is running?

The DTS instance reports an error and is interrupted. You can click the instance ID to view the instance details and modify the source or destination account password on the Basic Information tab. Then, go to the Task Management tab and restart the module that reported the error in the Basic Information section.

Why do some source or destination databases not have a public IP connection type?

This is related to the connection type of the source or destination database, the task type, and the database type. For example, for a source of the MySQL database type, migration and tracking tasks can choose to connect using a public IP address, while synchronization tasks do not support public IP connections.

Is cross-account data migration or data synchronization supported?

Yes. Configure a cross-Alibaba Cloud account task.

Can the source and destination databases be the same database instance?

Yes. If the source and destination are the same instance, use the mapping feature to isolate data. Otherwise, the DTS instance may fail or data may be lost. Database, table, and column mapping.

What is the latency metric of a DTS instance?

The latency of a DTS instance is normally within 1,000 milliseconds. If it exceeds 1,000 milliseconds, the DTS instance is in a delayed state. If the delayed state lasts for more than 5 minutes, the DTS instance service is considered unavailable.

Why does a task with Redis as the destination report the "OOM command not allowed when used memory > 'maxmemory'" error?

This may be because the storage space of the destination Redis instance is insufficient. If the architecture type of the destination Redis instance is cluster, it may also be that a shard has reached its memory limit. You need to upgrade the specifications of the destination instance.

How do I ask questions about DTS?

You can join the DTS customer communication DingTalk group (Group ID: 116655009709) on DingTalk (Download DingTalk) to ask questions.

What is the AliyunDTSRolePolicy access policy and what is it used for?

The AliyunDTSRolePolicy policy allows DTS to access cloud resources such as RDS and ECS under the current or cross accounts. It calls relevant cloud resource information when you configure a migration, synchronization, or tracking task. Grant DTS permissions to access cloud resources.

How do I perform RAM role authorization?

Can the account password entered for a DTS task be modified?

Why does a MaxCompute table have a "_base" suffix?

1. Initial schema synchronization.

   DTS synchronizes the schema definitions of the tables to be synchronized from the source database to MaxCompute. During initialization, DTS adds the `_base` suffix to the table names. For example, if the source table is `customer`, the table in MaxCompute becomes `customer_base`.

2. Initial full data synchronization.

   DTS synchronizes all historical data from the tables in the source database to the `_base` tables in MaxCompute. For example, data is synchronized from the `customer` table in the source database to the `customer_base` table in MaxCompute. This data serves as the baseline for subsequent incremental data synchronization.

   Note

   This table is also known as the full baseline table.

3. Incremental data synchronization.

   DTS creates an incremental log table in MaxCompute. The table name is the name of the destination table with the `_log` suffix, such as `customer_log`. DTS then synchronizes incremental data from the source database to this table in real time.

   Note

   For more information about the structure of the incremental log table, see Incremental log table schema.

What do I do if I cannot get the Kafka topic?

./bin/kafka-topics.sh --describe --zookeeper zk01:2181/kafka --topic topic_name

Can I build a MySQL instance locally as a secondary database for an RDS instance?

Yes, you can. You can use the data migration feature of Data Transmission Service (DTS) to configure real-time data synchronization from RDS to a local self-managed MySQL instance to achieve a primary-secondary architecture.

How do I copy data from an RDS instance to a newly created RDS instance?

You can select schema migration, full migration, and incremental migration as the migration types. Data migration between ApsaraDB RDS instances.

Does DTS support copying a database within an RDS instance to create a new database that is identical except for the database name?

Yes, it does. The object name mapping feature provided by DTS can be used to copy a database within an RDS instance to create a new database that is identical except for the database name.

What do I do if a DTS instance always shows a delay?

What do I do if the fields are all lowercase after synchronizing or migrating to the destination database in the legacy console?

You can use the new console and the destination database object name case policy feature. Destination database object name case policy.

Can a paused DTS task be resumed?

In general, a DTS task that has been paused for no more than 24 hours can be resumed normally. If the data volume is small, a DTS task that has been paused for no more than 7 days can be resumed normally. We recommend that you do not pause a task for more than 6 hours.

Why does the progress start from 0 after a task is paused and restarted?

After a task is restarted, DTS re-queries the completed data and then continues to process the remaining data. During this process, the task progress may differ from the actual progress due to latency.

What is the principle of DDL lockless change?

For the main principles of DDL lockless change, see Main principles.

Does DTS support pausing the synchronization or migration of a specific table?

No, it does not.

Do I need to repurchase a task if it fails?

No, you do not. You can reconfigure the original task.

What happens if multiple tasks write data to the same destination?

This may cause data inconsistency.

Why is the instance still locked after renewal?

After you renew a locked DTS instance, it takes some time for the instance to be unlocked. Please wait.

Can I change the resource group of a DTS instance?

Yes, you can. On the Basic Information page of the instance, click Modification next to Resource Group Name in the Basic Information area.

Does DTS have a binary log analysis tool?

No, DTS does not have a binary log analysis tool.

Is it normal for an incremental task to always show 95%?

Yes, it is. An incremental task is continuous and will not be completed. The progress will not reach 100%.

Why hasn't a DTS task been released after more than 7 days?

Occasionally, a frozen task may be saved for more than 7 days.

Can I modify the port of a created task?

This is not supported.

Can the RDS for MySQL instance mounted under PolarDB-X 1.0 in a DTS task be downgraded?

Downgrading is not recommended. Downgrading triggers a primary/secondary switchover, which may cause data loss.

Can the source or destination instance be upgraded or downgraded while a DTS task is running?

Upgrading or downgrading the source or destination instance while a DTS task is running may cause task latency or data loss. We do not recommend changing the specifications of the source or destination instance.

What is the impact of a DTS task on the source and destination instances?

Initial full data synchronization will occupy some read and write resources of the source and destination databases, which may increase the database load. We recommend that you perform full tasks during off-peak hours.

What is the approximate latency of a DTS task?

The latency of a DTS task cannot be estimated because it is limited by many factors, such as the running load of the source instance, the bandwidth of the transmission network, network latency, and the write performance of the destination instance.

If the Data Transmission Service console automatically jumps to the Data Management DMS console, how do I return to the legacy Data Transmission Service console?

In the DMS console, click the icon in the bottom-right corner, and then click to return to the previous version of the Data Transmission Service console.

Does DTS support data encryption?

DTS supports secure access to the source or destination database through Secure Sockets Layer (SSL) encryption to read data from the source database or write data to the destination database, but it does not support encryption of data in-transit during data transmission.

Does DTS support ClickHouse as a source or destination?

No, it does not.

Does DTS support AnalyticDB for MySQL 2.0 as a source or destination?

AnalyticDB for MySQL 2.0 is supported only as a destination, and the solution with AnalyticDB for MySQL 2.0 as the destination is not yet available in the new console. It can be configured only in the legacy console.

Why can't I see a newly created task in the console?

Can the grayed-out configuration items of a created task be modified?

This is not supported.

Does DTS support AnalyticDB for MySQL 5.0?

Yes, it does. AnalyticDB for MySQL 5.0 is AnalyticDB for MySQL Data Lakehouse Edition (3.0).

How do I configure latency alerts and thresholds?

DTS provides monitoring and alerting. Set alert rules for important metrics to track running status. Configure monitoring and alerting.

Can I view the cause of failure for a task that has failed for a long time?

No, you cannot. If a task has failed for a long time (for example, more than 7 days), the relevant logs are cleared, and the cause of failure cannot be viewed.

Can a task that has failed for a long time be restored?

No, it cannot. If a task has failed for a long time (for example, more than 7 days), the relevant logs are cleared and cannot be restored. You need to reconfigure the task.

What is the rdsdt_dtsacct account?

If you have not created the rdsdt_dtsacct account, it may have been created by DTS. DTS creates a built-in account rdsdt_dtsacct in some database instances to connect to the source and destination database instances.

How do I view information about heap tables, tables without primary keys, compressed tables, tables with computed columns, and tables with sparse columns in SQL Server?

What do I do if the schemas of the source and destination are inconsistent?

You can try using the mapping feature to map columns between source and destination. Database, table, and column mapping.

Does database, table, and column mapping support modifying the column type?

No, it does not.

Does DTS support limiting the read speed of the source database?

No, it does not. You need to evaluate the performance of the source database (such as whether the IOPS and network bandwidth meet the requirements) before the task runs. We also recommend that you run the task during off-peak hours.

How do I clean up orphaned documents in a MongoDB sharded cluster instance?

Deletion of DATABASE.COLLECTION range [{ KEY: VALUE1 }, { KEY: VALUE2 }) will be scheduled after all possibly dependent queries finish

db.getSiblingDB("admin").aggregate( [{ $currentOp : { allUsers: true, idleCursors: true } },{ $match : { type: "idleCursor" } }] )

How do I handle uneven data distribution in a sharded MongoDB cluster?

You can enable the Balancer feature and use pre-sharding to resolve data skew. Data skew occurs when most data is written to a single shard.

sh.shardCollection("phonebook.contacts", { last_name: "hashed" }, false, {numInitialChunks: 16384})

sh.splitAt("<db>.<coll>", {"<shardKey>":<split_value>})

sh.splitAt("test.test", {"id":0})
sh.splitAt("test.test", {"id":50000})
sh.splitAt("test.test", {"id":75000})

How do I set the number of instances displayed per page in the task list in the console?

1. Go to the data synchronization task list page in the destination region. You can do this in one of two ways.

   DTS console

   1. Log on to the DTS console.

   2. In the navigation pane on the left, click Data Synchronization.

   3. In the upper-left corner of the page, select the region where the synchronization instance is located.

   DMS console

   Note

   The actual steps may vary depending on the mode and layout of the DMS console. For more information, see Simple mode console and Customize DMS console layout and style.

   1. Log on to the DMS console.

   2. In the top menu bar, choose Data + AI > DTS (DTS) > Data Synchronization.

   3. To the right of Data Synchronization Tasks, select the region of the synchronization instance.

2. Scroll to the bottom of the page.

3. In the lower-right corner of the page, select Items per page.

   Note

   You can set Items per page to 10, 20, or 50.

What do I do if a DTS instance reports a ZooKeeper connection timeout?

Try restarting the instance to restore the connection. For instructions on how to restart an instance, see Start a DTS instance.

Why is a DTS CIDR block automatically re-added after being deleted in CEN?

This can occur if you use a Basic Edition transit router from Cloud Enterprise Network (CEN) to connect your database to DTS. If you create a DTS instance using this database, DTS automatically adds the server's IP address range to the corresponding router, even if you delete the DTS CIDR block in CEN.

Can DTS tasks be exported?

Not supported.

How do I use Java to call an OpenAPI?

Calling an OpenAPI in Java is similar to Python. Refer to the Python SDK call example. You can go to the Data Transmission Service DTS SDK page, select your desired programming language from All Languages, and view the sample code.

How do I use an API to configure the ETL feature for a synchronization or migration task?

Configure this feature using common parameters such as etlOperatorCtl and etlOperatorSetting in the Reserve parameter. Configure a DTS migration or synchronization task and Reserve parameter description.

Does DTS support Azure SQL Database?

Yes, it does. To use Azure SQL Database as the source database, set SQL Server Incremental Synchronization Mode to Polling and querying CDC instances for incremental synchronization.

Will the source database data be retained after DTS synchronization or migration is complete?

Yes. DTS does not delete data in the source database. If you no longer need the data in the source database, you can delete it manually.

Can the rate be adjusted after a synchronization or migration instance is running?

Yes, it can. Adjust the migration rate.

How do I open the Alibaba Cloud AI Assistant to ask about DTS features?

You can click the Learn About DTS Features button at the top of the task list page to open the Alibaba Cloud AI Assistant dialog box.

Does DTS support sampling data for synchronization or migration by time period?

No.

Do I need to manually create data tables in the destination database when synchronizing or migrating data?

For DTS instances that support database and table schema tasks (schema synchronization or schema migration), if Schema Synchronization is selected for Synchronization Types or Schema Migration is selected for Migration Types, you do not need to manually create data tables in the destination database.

Do the networks of the source and destination databases need to be connected when synchronizing or migrating data?

No, you do not.

Does DTS support automatic scaling?

DTS Serverless instances can automatically scale by adjusting instance resources. What is a DTS Serverless instance?.

Does the public cloud support TDDL?

No, it does not. If you have configured TDDL rules for the data to be synchronized or migrated, the task may fail.