IBM i data deletion

I know that in a windows environment when you delete a file you really just delete the directory entry that tells you the name of the file and where it is on disk, and that the data in the file still exists at that point and can be retrieved. Does the IFS on IBM i work the same way, and if so, is there a way to actually overwrite the data space associated with a file so it is unreadable? Same question for DB2. I know when a record is deleted its not really deleted because there are utilities that can undelete a record. And that a RGZPFM gets rid of deleted records but even doing that does it make all the deleted records unreadable on disk?

This question is in relation to a PCI-DSS Requirement 3 that states "Processes for secure deletion of data when no longer needed" and applies to even data that is encrypted. Instead of just deleting records from any database that has card holder data in it (encrypted) should the first step being updating the card data in the record to blanks first so the blanks are written to disk and then deleting the record? That way even if someone was able to access a deleted record the card data would not be there