Re: update Is Oracle update a direct update in-place?

Fengqing Zhou wrote:
>
> Hi!
>
> Sybase has direct update in-place and non-direct update in-place.
>
> Nondirect update in-place means a update is a DELETE followed by
> an INSERT.
>
> Direct update in-place means the record updated still keeps its original
> physical location after update.
>
> My understanding for Oracle update is:
> All updates in Oracle are "Sybase direct update in-place".
>
> Am I wrong?
>
> TIA,

Absolutely true. However Oracle will migrate or chain to another block if it doesn't have enough space. The original ROW_ID will stay the same though so logically the row will not have moved from its original place.

Different from Sybase (but correct me if am wrong) is the use in Oracle of rollback segments. With rollback segments, Oracle makes sure it can undo any change still not committed. Could it be that Sybase offers that type of non-direct update to make sure the log files are entered with the old value before changing to the new? I think the difference between the 2 DBMS comes from their internal management of undoing uncommitted changes.

Sylvie Bérubé
sberube_at_aircanada.ca Received on Sun Jan 12 1997 - 00:00:00 CST