Ensure that your JSON file is properly formatted and accessible. Double-check for correct syntax and structure, as well as the presence of all necessary fields required for your Teradata table.

Download and install the Teradata Tools and Utilities (TTU) package from the Teradata website. This will provide you with essential command-line tools such as BTEQ and FastLoad, which are required for data loading tasks.

Use the Teradata SQL Assistant or BTEQ to connect to your Teradata Vantage system and create a table that matches the structure of your JSON data. Ensure that the data types of the table columns correspond to those of the JSON fields.

```sql
CREATE TABLE target_table (
id INTEGER,
name VARCHAR(100),
age INTEGER
-- Add more columns as needed
);
```

Write a script in Python or another programming language to parse the JSON file and convert it into a CSV format. The CSV format is necessary because Teradata's FastLoad tool can efficiently load CSV data.

```python
import json
import csv

with open('data.json') as json_file:
data = json.load(json_file)

with open('data.csv', 'w', newline='') as csv_file:
csv_writer = csv.writer(csv_file)
# Write headers
csv_writer.writerow(['id', 'name', 'age'])
# Write data rows
for record in data:
csv_writer.writerow([record['id'], record['name'], record['age']])
```

Use the FastLoad utility to load the CSV data into your Teradata table. Create a FastLoad script that specifies the CSV file and the target table.

```plaintext
SESSIONS 4;
LOGON /,;

DATABASE ;

BEGIN LOADING target_table
ERRORFILES error1, error2;

DEFINE
id (INTEGER),
name (VARCHAR(100)),
age (INTEGER)
FILE=data.csv;

INSERT INTO target_table
VALUES (:id, :name, :age);

END LOADING;
LOGOFF;
```

Run the FastLoad script using the FastLoad command-line utility:
```bash
fastload < fastload_script.fld
```

After the FastLoad process completes, verify that the data has been imported correctly by querying the target table in Teradata. Use BTEQ or SQL Assistant to issue a SELECT statement.

```sql
SELECT FROM target_table;
```

Check the output to ensure that all records from the CSV file are present and correctly formatted.

Review any error tables generated during the FastLoad process. Address any issues such as data type mismatches or formatting errors. Optimize the process by adjusting FastLoad parameters like session numbers and error handling settings for better performance.

By following these steps, you can efficiently move data from a JSON file to Teradata Vantage without relying on third-party connectors or integrations.