Before performing data synchronization task, DTS performs a precheck on the source and destination databases. This topic describes the possible causes for the failed precheck of various items and solutions to them.

Precheck items Possible causes of failure Solution

Source Database Connectivity

Destination Database Connectivity

The database account or password is incorrect. Obtain the correct password and modify the database password of the source or destination database configured in the synchronization task. For more information, see Change the database password.
Source or destination database has access restrictions on source IP addresses.
  • If the source or destination database is MySQL, re-authorize the database account. The authorized IP address list must include the IP addresses of DTS servers. For more information about how to select the IP address of the DTS server, see Add the CIDR blocks of DTS servers to the security settings of on-premises databases.
  • If the source or destination database is SQL Server database, disable the firewall or disable triggers.
  • If the source or destination database is Oracle, Modify TCP.VALIDNODE_CHECKING the value to no and restart the process.
A firewall is configured for the server to which the source or destination database belongs. Turn off firewall.
Network interworking problem between DTS server and source or target database. You can submit a ticket to contact Alibaba Cloud engineers for assistance.
Source Database Version DTS does not support databases of the specified version. For more information about the database versions supported by DTS, see Database types, initial synchronization types, and synchronization topologies. Upgrades or downgrades the database version.
Destination Database Availability When the destination databases does not exist in the destination instance, DTS would automatically creates the databases, the creation may fail due to the following reasons:
  • The database name contains special characters other than lowercase letters, digits, underscores (_), or hyphens (-).
  • The character set of the database is other than utf8, GBK, latin1, or utf8mb4.
  • The destination database account configured in the data synchronization task does not have corresponding permissions.
Manually create a database that meets the requirements in the target instance or adjust the permissions of the database account.
Source Database Permissions The database account configured in data synchronization task does not have sufficient permissions.
Note The permissions required by each type of database are different. For more information, see the following cases: Overview of data synchronization scenarios.
Adjust the permissions of a database account.
Destination Database Permissions
Schema Name Conflict The object, such as database and table, has the same name as that in the target database.
Value of server_id in Source Database The value of server-id is not a integer greater than or equal to 2. Log on to the source database and modify the value of server-id . For more information, see Value of server_id in a source database.
Source Database Binary Logging The binlogging feature is not enabled for the source database. Log on to the source database and enable binlogging. For more information, see Source database binlogging.
Binlog Format of Source Database The Binlog format is not set to ROW for the source database. Log on to the source database and run set global binlog_format='ROW ';, and then restart the MySQL process.
Integrity constraint The Parent Tables of the Child Tables are not selected as the objects to be synchronized. This impairs the integrity of foreign key constraints.
Storage Engine The storage engine of the table to be synchronized is FEDERATED, MRG_MyISAM, or TokuDB. Log on to the source database, and set the storage engine of the table to InnoDB.
Character Set DTS does not support the character set of the objects to be synchronized (such as UCS2). Log on to the source database, and set the character set of tables to utf8, GBK, latin1, or utf8mb4.
Complex topologies DTS does not support the topology consisting of source and destination instances. For more information about the topologies supported by DTS and relevant precautions, see Synchronization topologies. Stop the task or wait for the conflict to complete before performing the data synchronization.
Password Format of MySQL Database Specify whether you set up the password with an old format for the source database. Change the format of the database password. For more information, see old_passwords.