Subject Re: [Firebird-Architect] Supported transaction isolation levels?
Author Thomas Steinmaurer
Hi Ann!

thanks a lot for your extensive answer!


> OK, that happens in READ COMMITTED also. Here's where they make their
> mistake:
> The isolation levels are different with respect to phenomena P1,
> P2, and P3. Table 8, “SQL-transaction isolation levels and the
> three phenomena” specifies the phenomena that are possible and
> not possible for a given isolation level.
> Table 8 — SQL-transaction isolation levels and the three phenomena
> Level P1 P2 P3
> READ UNCOMMITTED Possible Possible Possible
> READ COMMITTED Not Possible Possible Possible
> REPEATABLE READ Not Possible Not Possible Possible
> SERIALIZABLE Not Possible Not Possible Not Possible
> NOTE 63 — The exclusion of these phenomena for SQL-transactions
> executing at isolation level SERIALIZABLE is a consequence of the
> requirement that such transactions be serializable.
> Sigh. Our consistency transactions are better than repeatable read -
> they don't allow phantoms as defined in the standard. They do allow
> other non-serializable operations. So they're between repeatable read
> and serializable.

Did you mean consistency or concurrency transactions when talking about
repeatable read above?