Drop Backup Table

1. Understand the Need to Drop Backup Tables

• Purpose: Dropping the backup table is typically done to clean up space after the data load process is successfully completed, or when backups are no longer needed (based on your retention policy).
• Timing: This task should be performed after the data loading process has been completed and successfully verified, ensuring the backup is no longer required for recovery.

2. Define the Backup Table Naming Convention

• Backup tables follow a naming convention where they are named with the original target table’s name, appended with "_BCK".
• Example: For the target table TARG_NAME, the backup table would be TARG_NAME_BCK.

3. Prepare the SQL Command

• Use the following SQL command to drop the backup table:

·        DROP TABLE <%=odiRef.getTable("L","TARG_NAME","A")%>_BCK;

• Explanation of the Command:
• The DROP TABLE statement will remove the backup table from the database.
• The <%=odiRef.getTable("L","TARG_NAME","A")%> part refers to the specific target table in Oracle Data Integrator (ODI). It dynamically references the target table TARG_NAME in the current schema, and the suffix _BCK is added to identify the backup table.

4. Add the Drop Backup Table Task to the Workflow

• The drop operation should be added as a task in the workflow that runs after the data load process has been completed successfully.
• Ensure the task is executed only if the data load has been successful, to avoid accidental deletion of backup tables in case of errors during the data load.

5. Verify the Target Table Name in the Command

• Ensure that the target table name (TARG_NAME) is correctly referenced within the ODI script. The odiRef.getTable function will fetch the correct table name based on the parameters (in this case, "L" for the logical schema, "TARG_NAME" for the target table, and "A" for the alias).

6. Test the Drop Backup Table Task

• Before implementing it in a production environment, test the drop task in a development or staging environment to ensure that the backup table is being dropped correctly and that no unexpected issues arise.

7. Monitor the Task Execution

• After adding the task, monitor the execution logs to confirm that the backup table is dropped as expected.
• Ensure there are no errors related to permissions or table existence (e.g., the backup table may have been dropped earlier, and attempting to drop it again will cause an error).

8. Handle Missing Backup Table

• In some cases, the backup table might not exist (for example, if the backup process was skipped or failed). It’s a good practice to implement error handling to avoid failure when the backup table is missing:
• Example error handling:

BEGIN

    EXECUTE IMMEDIATE 'DROP TABLE <%=odiRef.getTable("L","TARG_NAME","A")%>_BCK';

EXCEPTION

    WHEN OTHERS THEN

        -- Handle missing table error

        NULL; -- No action needed if the table is not found

END;

9. Automate Cleanup Process

• Automating the drop task helps maintain a clean and organized data warehouse environment by removing unnecessary backup tables after the data load is complete.

10. Confirm Table Deletion

• Verify that the backup table has been dropped successfully by querying the database or checking the table list in the schema.
• Example query to check if the table exists:

o   SELECT table_name FROM user_tables WHERE table_name = '<TARG_NAME>_BCK';

• If no record is returned, the backup table has been successfully dropped.

By following these steps, you can safely drop backup tables in your data warehouse environment after the data load process, ensuring efficient space management and maintaining a clean database.