Solution

To ensure successful data migration, DTS checks whether DTS servers can connect to the destination database during precheck. This topic describes the causes of check failures and how to troubleshoot failures.

 

Causes

The connectivity check may fail due to the following reasons.

 

Solution

The database account or password is incorrect

Detection method

You can check whether the database account and password for the data migration task are correct for a device that can connect to the destination database.
Note: You can also verify the database account and database password on the server where the destination database resides.

 

Solution

Login DTS console, modify the data migration task, enter the correct database account and database password, and re-run the PreCheck.

 

The destination database disallows access from external IP addresses

Detection method

  • You can enter the database account and password specified for the data migration task on the server where the destination database resides. If the connection is successful, the destination database may disallow access from external IP addresses.
  • If the destination database is a MySQL database, you can use a MySQL client to connect to the database and run the following SQL statement for inspection: Check whether the authorized IP address list includes the CIDR blocks of DTS servers. For more information, see IP address whitelist to be added when you migrate, synchronize, or subscribe to an on-premises database.
    SELECT HOST FROM mysql.user WHERE user='[$Username]',password='[$Password]';
    Note: replace [$Username] with and [$Password] replace it with the account and password that are specified in the data migration task.
  • If the destination database is an SQL Server database, check whether a firewall is set up on the Server where SQL Server is installed, or whether the endpoint or triggers in the destination database disallow the access from the IP address.
  • If the destination database is an Oracle database, check the sqlnet.ora configuration file of the destination database. TCP.VALIDNODE_CHECKING is it yes. If the item is set to yes, the destination database disallows access from external IP addresses.

 

Solution

  1. Select a solution based on the type of the target database.
    • If the destination database is a MySQL database, run the following SQL statement to authorize the database account again:
      GRANT ALL ON . TO 'username'@''%' IDENTIFIED BY '[$Password]';
      Note: replace [$Username] with and [$Password] replace it with the account and password that are specified in the data migration task.
    • If the destination database is an SQL Server database, disable the firewall or triggers.
    • If the destination database is an Oracle database, modify the TCP.VALIDNODE_CHECKING for no, and restart the process.
  2. After performing the above repair operation, log in DTS console, and re-execute the pre-check.

 

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

Detection method

  • If the server where the destination database resides runs on Windows, find Windows Defender Firewall from the control panel to check whether a firewall is configured for the server.
  • If the server where the destination database is installed runs on Linux, use iptables -L command to check whether the server is configured with a firewall.

 

Solution

After the firewall is disabled, log on. DTS console, and re-execute the pre-check.

 

Network connectivity problem

If the connectivity check still fails after the troubleshooting, the network between DTS servers and the destination database may be unavailable. You can submit a ticket to contact Alibaba Cloud technical support personnel.

 

Application scope

  • Data Transmission Service (DTS)