Subject Re: firebird frozing ...
Author mk_delphi
Hi Alexander

I tried to help Alessandro, this add some
info to the fact:

> FB don't support Dirty Read isolation level
Looking at IBPP code I found that:

ReadDirty = ReadCommitted + Rec_Version
ReadCommitted = ReadCommitted + No_Rec_Version

I dont figure out why IBPP use this notation

> Sooner or later garbage collection starts (or
> even sweep

sweep is disabled (set to 0)

Alessandro told me that the same code work fine
under Windows2000 (? I dont use C++ so I cant test it)


Marco Kregar

--- In, "Alexander V.Nevsky"
<ded@h...> wrote:
> --- In, Alessandro GARDICH
> <gremlin@g...> wrote:
> > hi to all ...
> >
> > I have many problems with firebird and ibpp
> > firebird server simply stop to work !!!
> > the process 'fbserver' is still alive, cpu occupation to 0%, all
> clients stopped,
> > difficult to make new connection ... seem is in a deadlock :( ...
> Alessandro, I can read C programs in books like "Computers for
> idiots", no more, but some observations on you code:
> 1. FB don't support Dirty Read isolation level, it is substituted
> somewhat else by your access library, don't know to which one.
> 2. Seems you are trying to randomly update records. Nothing unusual
> you have many exceptions about lock conflicts (they are named
> deadlock even if it is simple conflict). In wait mode which you use
> scenario is:
> one transaction updated some record
> another transaction tried to do the same with this record and waits
> what first one will do - if rollback, then it will run further, if
> commit, it will raise exception.
> since you always commit, exception is always raised.
> About freeze - you run 10 fast applications which hammers data and
> some minutes creates a lot of versions (millions, I think) of the
> records in your table. Sooner or later garbage collection starts
> even sweep, if your setting for it is default 20 000 transactions)
> server is extremely busy identifying unneeded already versions and
> freeing space occupied by them. If your real application requires
> behaviour, I think you should re-examine it, no one RDBMS can do
> every one will fail by own mode - FB collecting garbage, MSSQL -
> stopping read practically all in sensible modes or impudently lying
> read in Dirty mode.
> Best regards, Alexander.