Modify...to Truncated Option
To delete all the rows in the table and release the file space back to the operating system, specify modify...to truncated. For example, the following statement deletes all rows in the "acct_payable" table and releases the space:
modify acct_payable to truncated;
Using truncated converts the storage structure of the table to heap. You cannot specify any of the with_clause options when you modify to truncated.