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From "RPost" <rp0...@pacbell.net>
Subject Re: Derby architecture/design documents
Date Mon, 07 Feb 2005 02:19:33 GMT
> "Dibyendu Majumdar" wrote:

> . . . The forward change from A to B (redo) and the reversal of B to A
(undo) are both recorded as updates to the system.

At what point does a change from A to B cause the creation of a log/recovery
record?

For example, if a column has a current value of A and the change to B would
cause a violation of a check, unique or foreign key constraint will a log
record be created or will the change have already been rejected?

There will potentially be more complicated scenario's where a change causes
a trigger, or other side effect, to be executed. Generally speaking, at what
point do the log/recovery records for these multiple changes get created?
Only if the attempted changes meet all of the criteria for acceptance? That
is, only if they would be accepted were a COMMIT to be performed?


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