Before starting the data migration process, ensure that your IBM Db2 environment is properly configured and accessible. Verify that you have the necessary permissions to extract data and that the database is in a consistent state. Identify the tables and data that need to be migrated by generating a list of schemas, tables, and relevant columns.

Utilize the Db2 EXPORT utility to extract data from the selected tables into a flat file format such as CSV. This can be done using the following Db2 command:
```sql
EXPORT TO 'data.csv' OF DEL MODIFIED BY NOCHARDEL SELECT FROM your_table;
```
Make sure to handle data types and ensure that special characters and delimiters are correctly managed to avoid issues during import.

Once the data is exported into flat files, transfer these files to the Teradata environment. This can be done using secure file transfer protocols such as SCP, SFTP, or using physical media if necessary. Ensure that the target location has sufficient storage and appropriate permissions for file access.

Set up the Teradata environment to receive the data. Create the necessary database schema, tables, and define the appropriate data types that correspond to the source schema in Db2. This can be done using Teradata SQL commands to create tables that match the structure of those in Db2.

Use the Teradata BTEQ (Basic Teradata Query) utility to load data from the flat files into the Teradata tables. The BTEQ script should include commands to read data from the files and insert them into the corresponding Teradata tables, like so:
```sql
.LOGON your_teradata_server/username,password;
.IMPORT DATA FILE = 'data.csv';
REPEAT;
USING (column1 VARCHAR(100), column2 INT, ...)
INSERT INTO your_teradata_table (column1, column2, ...)
VALUES (:column1, :column2, ...);
.LOGOFF;
```

After loading the data, perform data validation to ensure that the migration was successful. Run SQL queries to count records, check for duplicates, and compare sample data between Db2 and Teradata. Consider using checksums or hash values for data comparison to verify accuracy.

Once data integrity is confirmed, optimize the newly imported data in Teradata by collecting statistics and updating indexes. This can improve query performance and ensure efficient data retrieval. Execute commands such as:
```sql
COLLECT STATISTICS ON your_teradata_table;
```
Review the database setup and perform any necessary maintenance tasks to finalize the migration process.