>>> Hi. In highly concurrent environment, part of an app is using .NET RepeatableRead transaction to read data from few tables.
>>> I noticed that during these reads, writers to these tables experience major slowdown.
>>> So question is this:
>>> Does (Concurrency,ReadWrite) (.NET RepeatableRead) has major impact writers?
>>
>> I'm not familiar with the .NET driver ...
>>
>> * What does "major slowdown" mean?
>> * Is repeatable read involved for all transactions or read committed as
>> well?
>> * If read committed, are you using REC_VERSION or no record versions?
>> * Do you use WAIT or NO WAIT at transaction level?
>> * Do you end up with long running transactions? What does gstat -h and
>> or the monitoring tables say?
>> * When committing. Do you use commit retaining or "hard" commits?
>>
>> More questions than answers ... ;-)
>>
>>
>> --
>> With regards,
>> Thomas Steinmaurer
>> http://www.upscene.com/
>>
>> Professional Tools and Services for Firebird
>> FB TraceManager, IB LogManager, Database Health Check, Tuning etc.
>>
> First thank you for your time.
> It seems that .NET Repeatable read translates to
> Concurrency, Write, NoWait
> Id does not specify RecVersion, so it defaults to something.

REC_VERSION / NO_REC_VERSION only applies to read committed isolation level.

> If it defaults to NoRecVersion, then it seems understandable that
> this transaction possibly waits for concurrent writers to commit, which would explain slow writes and slow execution of this transaction.
>
> I need readonly snapshot of few related tables, so i figure that
> Concurrency, Read, NoWait, RecVersion would be solution.
>
> Any opinoon on this?
> And again, thanks for your time...

Make use of read-only transactions, if you can. Even being read-only,
read-only long-running repeatable read transactions will block garbage
collection, so make sure to not keep them open all day long.

Read-only / read committed is the less intrusive combination available
in Firebird though.


--
With regards,
Thomas Steinmaurer
http://www.upscene.com/

Professional Tools and Services for Firebird
FB TraceManager, IB LogManager, Database Health Check, Tuning etc.