DTS checks whether DTS servers can connect to the source database during the precheck to ensure successful data migration. This topic describes causes of check failure and how to fix the failure.

The following shows the potential causes of the failed source database connectivity check.

The database account or password is incorrect

Troubleshooting:

Get a device that can connect to the source database. On the device, enter the database account and password that are specified in the data migration task to check whether the account or password is correct.
Note You can also check the account and password on the server where the source database resides.

Solution:

Log on to the DTS console, enter the correct account and password, and perform another precheck.

The IP address used to access the source database is disallowed to access the database

Troubleshooting:

  • You can enter the account and password that are specified in the data migration task on the server where the source database resides and connect to the database. If the connection is successful, it indicates that the source database disallows the access from the IP address.
  • If the source database is a MySQL database, you can use a MySQL client to connect to the database and run the following command.
    SELECT HOST FROM mysql.user WHERE user='username',password='password';
    Note Replace the username and password with the account and password that are specified in the data migration task.

    Check whether the authorized IP address list includes the IP addresses of the DTS servers. For more information, see Add the CIDR blocks of DTS servers to the security settings of on-premises databases.

  • If the source database is an SQL Server database, check whether a firewall is set up for the server where the database resides. In addition, check whether the endpoint or triggers in the source database disallows the access from the IP address.
  • If the source database is an Oracle database, check whether the TCP.VALIDNODE_CHECKING item in the sqlnet.ora configuration file is set to yes. If the item is set to yes, it means that the source database disallows the access from the IP address.

Solution:

  • If the source database is a MySQL database, run the following command to reauthorize the database account.
    GRANT ALL ON . TO 'username'@''%' IDENTIFIED BY 'password';
    Note Replace the username and password with the account and password that are specified in the data migration task.
  • If the source database is an SQL Server database, disable the firewall or triggers.
  • If the source database is an Oracle database, set the TCP.VALIDNODE_CHECKING item to no and restart the process.

Log on to the DTS console to perform another precheck.

A firewall is configured for the server where the source database resides

Troubleshooting:

  • If the server where the source database resides runs Windows, find Windows Defender Firewall from the Control Panel to check whether a firewall is configured for the server.
  • If the server where the source database resides runs Linux, run the iptables -L command in the shell to check whether a firewall is configured for the server.

Solution:

After you disable the firewall, log on to the DTS console to perform another precheck.

Network connections fail

If the connectivity item still cannot pass the precheck after the preceding troubleshooting, network connections between the DTS server and the source database may not function as expected. Submit a ticket to contact Alibaba Cloud engineers.