The ORA-12170: TNS:Connect timeout occurred error typically indicates that the database link is unable to establish a connection to the target database within the specified timeout period. This can happen due to various reasons. Here are some steps you can take to troubleshoot and resolve the issue:

Check network connectivity:

Ensure that the security groups and network ACLs allow traffic between the two RDS instances. Verify that the VPCs in both accounts are properly connected (e.g., via VPC peering or AWS Transit Gateway). Verify DB link configuration:

Double-check the DB link configuration, including the hostname, port, and service name. Ensure that the username and password used in the DB link are correct and have the necessary permissions. Check RDS instance status: