Before data migration, Data Transmission Service (DTS) tests the connectivity between DTS servers and the target database. This topic lists common causes of check failures and how to troubleshoot these failures.

The connectivity check may fail due to the following reasons.

The database account or password is incorrect

Troubleshooting:

To verify that the specified account and password are correct, you can log on to the target database from a remote database client, using the account and password.

Solution:

Log on to the DTS console, enter the correct database account and password, and then perform a precheck again.

The target database blocks access from external IP addresses

Troubleshooting:

  • If your target database is a user-created database, you can log on to the server that hosts the database system and initiate a database logon session locally from that server. If you can log on locally from the target server, it means that the target database does not allow access from external IP addresses.
  • If the target database is a MySQL database, you can use a MySQL client to connect to the database and run the following statement:
    SELECT HOST FROM mysql.user WHERE user='username',password='password';
    Note Replace the username and password placeholders with the database account and password specified for the data migration task.

    Check whether the authorized IP address list includes the IP address ranges of DTS servers. For more information, see Whitelist DTS IP addresses for your user-created database.

  • If the target database is an SQL Server database, check whether a firewall is enabled for the server where the database resides. You can also check whether endpoints or triggers in the target database disallow access from external IP addresses.
  • If the target database is an Oracle database, check whether the TCP.VALIDNODE_CHECKING parameter in the sqlnet.ora configuration file is set to yes. If the paremeter is set to yes, the target database blocks access from external IP addresses.

Solution:

  • For a target MySQL database: run the following statement to authorize the database account again:
    GRANT ALL ON *.* TO 'username'@''%' IDENTIFIED BY 'password';
    Note Replace the username and password placeholders with the database account and password specified for the data migration task.
  • For a target SQL Server database: disable the triggers that block access from external IP addresses. Additionally, add DTS IP address ranges to the firewall rules or temporarily disable the firewall during migration.
  • For a target Oracle database: set the TCP.VALIDNODE_CHECKING parameter to no and restart the Oracle Net Listener process.

Log on to the DTS console to perform a precheck again.

A firewall is enabled on the target database server

Troubleshooting:

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

Solution:

Add DTS IP address ranges to the firewall rules or temporarily disable the firewall during migration. Then, log on to the DTS console to perform a precheck again.

The network is unavailable

If the connectivity check failure persists after you perform the preceding troubleshooting steps, the network between DTS servers and the source database may be unavailable. You can contact Alibaba Cloud Customer Services by submitting a ticket.