First, ensure you have a compatible environment where both Oracle Database and Apache Iceberg can operate. Install the necessary Oracle client on the machine where you'll be running the data export process. Additionally, ensure that you have a setup with Apache Hadoop or an equivalent file system that supports Apache Iceberg.

Use Oracle SQL*Plus or SQL Developer to run SQL queries that extract the desired data. You can use the `SPOOL` command in SQL*Plus to export data to a CSV file. For example:
```sql
SPOOL '/path/to/exported_data.csv';
SELECT * FROM your_table;
SPOOL OFF;
```

After exporting, ensure the data format is compatible with Apache Iceberg. Typically, this means converting your CSV data into a columnar format like Parquet, which Iceberg natively supports. Use a script to read the CSV file and convert each row into the Parquet format.

Create a new table in Apache Iceberg to store the data. This involves setting up a Hive Metastore or a compatible catalog that Iceberg can use. Use the SQL syntax from the Apache Iceberg documentation to define the table schema and location.

Use Apache Spark or Apache Flink to load the Parquet data into the Iceberg table. Start an instance of Spark or Flink with the Iceberg libraries included, and write a simple job to read the Parquet file and write it into the Iceberg table. For example, in Spark:
```python
spark.sql("CREATE TABLE iceberg_db.my_table USING iceberg")
df = spark.read.parquet("/path/to/parquet_data")
df.write.format("iceberg").mode("append").save("iceberg_db.my_table")
```

Once the data is loaded into the Iceberg table, run queries to validate that all data was transferred correctly. Check row counts and sample data from both the original Oracle table and the new Iceberg table to ensure accuracy.

Finally, optimize the Iceberg table for performance by compacting small files and performing any necessary maintenance tasks, such as updating statistics. Use the maintenance functions provided by your processing engine (e.g., Spark) to regularly maintain the Iceberg table.
By following these steps, you will have successfully moved data from Oracle DB to Apache Iceberg, leveraging standard tools without relying on third-party connectors or integrations.