Object Deletion (cont.)
An alternative (not available in O2): Allow explicit object deletion at any time
Replace the physical object with a tombstone
- Tombstone is a special marker (similar to a NULL)
- When some object follows an OID to the deleted object, it encounters the tombstone
- The reference that was just followed can be set to NULL or some default value or other action taken
This approach can make implementation of SET NULL semantics, etc. much easier!!!
Avoids the dangling references problem