Object Identification Number Limitations

This section covers three limitations of object identification numbers.

Nonsequential Numbering

The global nature of object identification assignment means most OIDs in a table are not sequential. For example, if you insert one customer today, and another one tomorrow, the two customers will not get sequential OIDs. In fact, their OIDs could differ by thousands because any INSERTs into other tables between the two customer inserts would increment the object counter. If the OID is not visible to users, this gap in numbering is not a problem. The nonsequential numbering does not affect query processing. However, if users can see and enter these numbers, it might seem strange that customer identification numbers are not sequential and have large gaps between them.

Nonmodifiable

An OID is assigned to every row during INSERT . UPDATE  cannot modify the system-generated OID of a row.

Not Backed Up by Default

 During database backups , the system-generated OID of each row is normally not backed up. A flag must be added to enable the backup of OIDs. See Section  for details.