Error code 231001 indicates a connection issue between the Database/Instance and the backup server. This critical error message reads, "Unable to establish the connection between the Database/Instance and the backup server." This knowledge base article offers troubleshooting guidelines for resolving this problem when dealing with backups for Microsoft SQL Server, MySQL Server, and PostgreSQL Server.

1. Credential Validation Issue: Verify the accuracy of the MSSQL Instance credentials used for the backup.

2. MSSQL Server Inactive: Check if the MSSQL Service is running on the server. The server must be active for backups to occur. 

3. Insufficient User Permissions: Assess whether the login account under which the agent is operating has sufficient permissions to access and back up the MSSQL Server.

4. Network Issue: Ensure that a connection has been established between the BDRSuite backup server and the BDRSuite backup agent.

1. Credential Validation Issue: Ensure the accuracy of the Database Instance credentials used for the backup.

2. Executable Path Validation: Check the validity of the file paths for the MySQL executable ("mysql") and the MySQL dump utility executable. These paths must be correct for successful backups.

3. MySQL Server Inactive: Verify if the MySQL Service is running on the server. The MySQL server must be active during backup operations.

4. Inadequate User Permissions: Evaluate whether the login account utilized by the agent possesses the required permissions to access and back up the MySQL Server.

5. Port Number Verification: Confirm the correctness of the provided port number for the running MySQL server. The port number should be accurate for successful connections.

6. Network Issue: Ensure that a connection has been established between the BDRSuite backup server and the BDRSuite backup agent.

1. Credential Validation Issue: Validate the accuracy of the Database Instance credentials used for the backup.

2. Executable Path Validation: Check the validity of the file paths for the PostgreSQL executables ("psql" and "pg_dump"). Ensure that these paths are correct for the backup process.

3. PostgreSQL Server Inactive: Ensure that the PostgreSQL service is running on the server. A running PostgreSQL server is necessary for successful backups.

4. Inadequate User Permissions: Examine whether the login account used by the agent has the required permissions to access and back up the PostgreSQL Server.

5. Port Number Verification: Confirm the correctness of the provided port number for the running PostgreSQL server. The port number should be accurate for proper connections.

6. Network Issue: Ensure that a connection has been established between the BDRSuite backup server and the BDRSuite backup agent.

6. Peer Authentication: The error occurs because psql, by default, uses peer authentication over UNIX sockets. To backup the PSQL database using our application you need to enable password authentication over Unix sockets instead of peer authentication.

Troubleshooting Steps:

To enable password authentication over Unix sockets instead of peer authentication, you can modify the 'pg_hba.conf' file.

  Change the line from:

    # TYPE DATABASE USER ADDRESS METHOD

         local          all                 all                     peer

  To:

    # TYPE DATABASE USER ADDRESS METHOD

         local          all                 all                    md5

After making changes to 'pg_hba.conf,' restart the PostgreSQL service to apply the modifications. You can use a command like 'sudo service postgresql restart.'