Subject Re: [firebird-support] Re: what is the most fastest isolation level ?
Author Thomas Steinmaurer
Hello Dmitry,

> n> no one have an idea about what is a
> n> deadlock
> n> Error: 16
> n> ?
> n> the isolation of the transaction was: isc_tpb_read_committed +
> n> isc_tpb_no_rec_version + wait => normally no deadlock must appear ??
> Maybe you have 2 wait transactions that locks each other.
> Since you are using no_read_committed, it "locks" even
> on reading, so, any reading in trigger, etc, can cause
> real deadlock (since you said that you have "ddl is a little long").
>>> i know the behavior of each, but i need to know the difference in speed / resource usage between each of them ...
> no speed difference or resource usage between rec_version and
> no_rec_version. And even more, I can say that only shapshot
> (concurrency, consistency) transactions consume resources, and
> resourses is the size of local copy of TIP for that transaction.
> n> what is the most fastest isolation level ?
> No one. When transaction works alone, none difference in speed, for
> any isolation level. Versioning engine doesn't place any locks
> somewhere in DB or memory.
> But, when you start update and delete records, you produce
> versions, and here is the main performance source - there more
> versions transaction reads to understand what it can show
> and what not to show, the slower reading will be.
> For me no_rec_version itself is the worst case, nearly useless.
> I even wonder why it exist

To simulate SQL Server 2000 concurrency capabilities? Sorry, could not
resist. ;-)