IBM added a feature with V2R1M0 that allows the reusing of deleted records in a physical file without a reorganization. Unfortunately, they have put a restriction on this new feature that renders it virtually worthless. You cannot have a file reuse deleted records if the file has any logicals over it that specify FIFO or LIFO ordering for duplicate keys, or if the physical file has a FIFO or LIFO duplicate key ordering.
Since duplicate key ordering requires you to have FIFO or LIFO ordering, the only files available that would allow the reuse of deleted records are those with only unique keys. In my experience, that is not very many files.
Editor's Note: Unique keys cannot be used with most logical files, since you have an almost complete assurance that there will be duplicate keys. Therefore, you cannot reuse deleted records in any physical files that have logical files built on top. How many files is that?