Ensure that you have access to the Oracle database, including the necessary credentials (username, password) and the database connection string. Install the Oracle Instant Client if it's not already available, as it provides the necessary libraries to connect to and interact with Oracle databases.

Install Python on your local machine if it's not already installed. Use a package manager like `pip` to install the `cx_Oracle` library, which is used to connect to Oracle databases in Python. You can do this by running the command:

```bash
pip install cx_Oracle
```

Write a Python script to establish a connection to your Oracle database using the `cx_Oracle` library. Use the credentials and connection string from Step 1 to create the connection. Here's a sample code snippet:

```python
import cx_Oracle

# Database credentials
username = 'your_username'
password = 'your_password'
dsn = 'your_dsn' # Data Source Name

# Establishing the connection
connection = cx_Oracle.connect(user=username, password=password, dsn=dsn)
```

Once connected, write a SQL query to fetch the data you want to transfer into a JSON file. Execute this query using the cursor object provided by `cx_Oracle`. Here's an example:

```python
cursor = connection.cursor()
query = "SELECT FROM your_table"
cursor.execute(query)
rows = cursor.fetchall()
```

Use Python's built-in `json` library to convert the fetched data into JSON format. First, fetch the column names, then iterate over the rows and construct a list of dictionaries representing the data.

```python
import json

columns = [col[0] for col in cursor.description]
data = [dict(zip(columns, row)) for row in rows]
```

With the JSON-formatted data ready, write it to a local file. Specify the file path where you want to save the JSON file. Use the `json.dump` function to write data to the file with pretty formatting.

```python
with open('output.json', 'w') as json_file:
json.dump(data, json_file, indent=4)
```

After the data has been successfully written to the JSON file, ensure you close the database connection and any open cursors to free resources and avoid potential memory leaks.

```python
cursor.close()
connection.close()
```

By following these steps, you can efficiently move data from an Oracle database to a local JSON file without the need for third-party connectors or integrations.