Begin by ensuring that you have the necessary access rights to the Oracle database. Verify that you can connect to the database and have the necessary permissions to read the data you intend to export. Identify the tables and data types you need to move to ClickHouse.

Use Oracle’s SQL Developer or SQL*Plus to export the data from the Oracle database into CSV files. You can use a SQL query to select the required data and redirect the output to a CSV file. Here's a basic example using SQL*Plus:
```sql
SPOOL output.csv
SELECT * FROM your_table;
SPOOL OFF;
```
Adjust the query and file paths as needed.

Once the CSV files are generated, transfer them to the server where ClickHouse is installed. You can use secure copy (SCP), FTP, or any other method to move files securely between servers. Ensure the files are placed in a directory that ClickHouse can access.

Before importing data, create the necessary tables in ClickHouse. Define the tables with the appropriate schema that matches the data types and structure of the Oracle tables. Use ClickHouse's `CREATE TABLE` syntax for this purpose:
```sql
CREATE TABLE your_clickhouse_table (
column1 DataType,
column2 DataType
) ENGINE = MergeTree()
ORDER BY column1;
```
Adjust columns and data types to match the structure of your Oracle data.

Use ClickHouse's native client or HTTP interface to import data from the CSV files into ClickHouse tables. Here is an example command using the ClickHouse client:
```bash
clickhouse-client --query="INSERT INTO your_clickhouse_table FORMAT CSV" < /path/to/your/csvfile.csv
```
Ensure that the CSV file path is correct and accessible by ClickHouse.

After importing the data, perform checks to ensure data integrity. Run queries to compare row counts and sample data between the Oracle database and ClickHouse. This step ensures that the data has been accurately transferred:
```sql
SELECT COUNT(*) FROM your_clickhouse_table;
```

Finally, optimize the ClickHouse tables to ensure efficient data retrieval and performance. You can use the `OPTIMIZE TABLE` command to merge parts and improve query performance:
```sql
OPTIMIZE TABLE your_clickhouse_table FINAL;
```
Conduct performance testing to ensure that the data access meets your requirements.
By following these steps, you can successfully move data from an Oracle Database to ClickHouse without relying on third-party connectors or integrations.