Before DTS runs a data synchronization task, DTS performs a precheck on the source and destination databases. This topic describes how to troubleshoot precheck failures based on the causes.

Precheck item Cause of failure Solution

Source database connectivity

Destination database connectivity

The database account or password is invalid. Obtain the valid password, and change the password of the source or destination database in the DTS console. The password is specified when you configure the data synchronization task. For more information, see Change the password of a database account.
The IP address that is used to access the source or destination database is disallowed to access the database.
  • For a MySQL database, authorize the database account again. The CIDR blocks of DTS servers must be added to the IP whitelist. For more information about the CIDR blocks of DTS servers in each region, see Add the CIDR blocks of DTS servers to the security settings of on-premises databases.
  • For an SQL Server database, disable the firewall or trigger settings.
  • For an Oracle database, set the TCP.VALIDNODE_CHECKING parameter to no and restart the process.
A firewall is configured on the server where the source or destination database resides. Disable the firewall settings.
The network between DTS servers and the source or destination database is unavailable. Contact Alibaba Cloud engineers for technical support. For more information, visit submit a ticket .
Source database version DTS does not support the current database version. For more information, see Database types, initial synchronization types, and synchronization topologies. Upgrade or downgrade your database version.
Database existence If the destination database does not exist in the destination instance, DTS may fail to create a database because of the following reasons:
  • The database name contains special characters except letters, digits, underscores (_), and hyphens (-).
  • The character set of the database is not UTF8, GBK, Latin1, or UTF8MB4.
  • The account that is used to access the destination database does not have the required permissions.
Create a database in the destination instance or grant the required permissions to the database account.
Source database permissions The account that is used to access the source or destination database does not have the required permissions.
Note The permissions that are required for a database vary with the database type. For more information, see Overview of data synchronization scenarios.
Grant the required permissions to the database account.
Destination database permissions
Schema name conflict The source and destination databases have the same name, or the source and destination tables have the same name.
Value of server_id in the source database The value of the server-id parameter is not set to an integer that is greater than or equal to 2. Log on to the source database and change the value of the server-id parameter. For more information, see Value of server_id in a source database.
Whether binary logging is enabled for the source database The binary logging feature is disabled for the source database. Log on to the source database and enable the binary logging feature. For more information, see Source database binlogging.
Binary log format of the source database The binary log format of the source database is set to ROW. Log on to the source database, run the set global binlog_format='ROW'; command, and then restart the MySQL process.
Integrity of FOREIGN KEY constraint The parent table on which a child table depends is not included in the required objects. This impairs the integrity of the FOREIGN KEY constraint.
Storage engine The storage engine of the source table is FEDERATED, MRG_MyISAM, or TokuDB. Log on to the source database and set the storage engine of the source table to InnoDB.
Character set DTS does not support the character set of the required objects, such as UCS2. Log on to the source database and set the character set of source tables to UTF8, GBK, Latin1, or UTF-8MB4.
Complicated topologies DTS does not support the topology that you use for the source and destination instances. For more information, see Synchronization topologies. Stop the conflicting task or wait for the task to complete, and then perform data synchronization again.
Format of MySQL database password The format of the password that is used to access the source database is no longer valid. Change the format of the database password. For more information, visit old_passwords.