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. ;-) Regards, Thomas
