"Ann W. Harrison" <aharrison@...> wrote:

>
> >> Read-committed mode violates the Isolation and Consistency
> >> properties of transactions
>
> [snip]
>
> Consistent - when it executes the same query twice,
> the only changes it sees are the changes it made

Consistency refers to the database being in a legal state when the
transaction begins and when it ends. This means that a transaction can't
break the rules, or integrity constraints, of the database.

> Isolated - actions of concurrent transactions do no
> affect it

Isolation refers to the ability of the application to make operations in a
transaction appear isolated from all other operations. This means that no
operation outside the transaction can ever see the data in an intermediate
state.

> Read-committed transactions see the changes made by concurrent
> transactions - they're not consistent.

Formally, I disagree (see above).


Dmitry