IDS Forum

Re: What log size is too large?

Posted By: Fernando Nunes
Date: Thursday, 10 November 2016, at 6:40 a.m.

In Response To: Re: What log size is too large? (Art Kagel)

No Art. As you say you do it when you backup the log. That's in the "end of
the log". What I'm taling about (and we do with HDR synchronous) it to
replicate each transaction. We don't wait for the end of log.
It's the difference between being able to recover on a logical log based
unit, or on a transaction based unit. Completely different.
Regards.

On Thu, Nov 10, 2016 at 11:31 AM, Art Kagel <art.kagel@gmail.com> wrote:

> Fernando:
>
> Whenever I set up an alarmprogram to backup the logical logs to disk (so
> not using a storage manager) I also copy the log back up file to another
> machine for immediate safety. Often that's the HDR secondary's machine but
> some clients prefer that the remote copy go elsewhere. If you are using
> onbar and a storage manager for log backups, that is the same thing, just
> more formalized. Either way this is essentially the kind of log only
> replica you are talking about. So we can do it with Informix too. It's just
> so obvious that like many things that the "other guy" thinks are cool
> features, we just do and don't talk about.
>
> Art
>
> Art S. Kagel, President and Principal Consultant
> ASK Database Management
> www.askdbmgt.com
>
> Blog: http://informix-myview.blogspot.com/
>
> Disclaimer: Please keep in mind that my own opinions are my own opinions
> and do not reflect on the IIUG, nor any other organization with which I am
> associated either explicitly, implicitly, or by inference. Neither do
> those opinions reflect those of other individuals affiliated with any
> entity with which I am affiliated nor those of the entities themselves.
>
> On Thu, Nov 10, 2016 at 6:04 AM, Fernando Nunes <domusonline@gmail.com>
> wrote:
>
> > Just to add up... at least one of our competitors can do something
> > interesting.... they can create a "replica" which doesn't have data, but
> > works to receive the logical logs.
> > It's a relatively easy way to have a remote copy of the logs which can be
> > used for recover of a catastrophic situation on the primary site.
> > It would be a bit like if we setup a secondary server, without dbspaces
> and
> > with "STOP_APPLY" active. the logs would be cached on a directory... this
> > would be a nice RFE if someone feels the need.
> >
> > Regards.
> >
> > On Thu, Nov 10, 2016 at 10:59 AM, Fernando Nunes <domusonline@gmail.com>
> > wrote:
> >
> > > I totally agree with Art's answer and I don't understand how bigger
> logs
> > > will give you better performance apart that if you change logs very
> > quickly
> > > the overhead of onbar handshake with the storage manager may become an
> > > issue. But this would be a thing to consider if you chnage logs every
> few
> > > seconds...
> > >
> > > Also note that the discussion about "how long can you afford to loose"
> is
> > > not an easy discussion within customers. The natural answer is
> "nothing"
> > > which can't be done unless you have a replica and that replica is
> > > synchronous. And in reality I've never faced a situation where "a bomb
> > hit
> > > the datacenter completely destroying the machine". And also not that in
> > > that catastrofic situation, a local replica would not be very useful...
> > and
> > > a remote synchronous replica could have serious performance
> implications.
> > >
> > > I guess that what I'm trying to say is that there will always be margin
> > for
> > > data loss... unless you're willing to pay a very costly price for
> > something
> > > that really would never happen, and honestly, if it ever happened
> people
> > > would have a lot more to be concerned with. So... the discussion is not
> > > easy. But normally people accept a very reduced risk for a couple of
> > > minutes. Actually I'll have a discussion like this tomorrow... so I
> think
> > > I'm preparing myself for it ;)
> > >
> > > Regards
> > >
> > > On Wed, Nov 9, 2016 at 9:58 PM, Lester Knutsen <
> > > lester@advancedatatools.com>
> > > wrote:
> > >
> > > > Kate,
> > > >
> > > > Smaller logs give you better recoverability, larger logs are better
> > > > performance. My recommendation for OLTP systems is to setup a logs so
> > you
> > > > are
> > > > going through one log every 5 to 10 minutes, which it sounds about
> like
> > > > what
> > > > you have , so if you lost your system and the current log, you could
> > > > recover
> > > > from a log backup about 5 to 10 minutes ago. If you don't need to
> worry
> > > > about
> > > > recoverability, then the bigger logs will be faster and I have use
> > 500MB
> > > > logs.
> > > >
> > > > Regards - Lester
> > > >
> > > > On 11/9/16 4:35 PM, Kate Tomchik wrote:
> > > > > We have a system with logs sized at 200MB. We are rolling through 6
> > or
> > > > > more of those every hour. We are considering go to 500MB. Does
> anyone
> > > > > have logs that large out there?
> > > > >
> > > >
> > > > --
> > > > ____________________________________________________________
> __________
> > > > Lester Knutsen lester@advancedatatools.com
> > > > Advanced DataTools Corporation Voice: 703-256-0267 x102
> > > > Visit our Web page: http://www.advancedatatools.com
> > > > ____________________________________________________________
> __________
> > > >
> > > >
> > > > ************************************************************
> > > > *******************
> > > > Forum Note: Use "Reply" to post a response in the discussion forum.
> > > >
> > > >
> > >
> > > --
> > > Fernando Nunes
> > > Portugal
> > >
> > > http://informix-technology.blogspot.com
> > > My email works... but I don't check it frequently...
> > >
> > > --001a11446e8629eb800540f04396
> > >
> > >
> > > ************************************************************
> > > *******************
> > > Forum Note: Use "Reply" to post a response in the discussion forum.
> > >
> > >
> >
> > --
> > Fernando Nunes
> > Portugal
> >
> > http://informix-technology.blogspot.com
> > My email works... but I don't check it frequently...
> >
> > --001a113fbb5ac398f10540f05521
> >
> >
> > ************************************************************
> > *******************
> > Forum Note: Use "Reply" to post a response in the discussion forum.
> >
> >
>
> --bcaec508f4bceb75250540f0b73b
>
>
> ************************************************************
> *******************
> Forum Note: Use "Reply" to post a response in the discussion forum.
>
>

--
Fernando Nunes
Portugal

http://informix-technology.blogspot.com
My email works... but I don't check it frequently...

--94eb2c0651e27c9c1a0540f0d3a5

Messages In This Thread

• What log size is too large?
  Kate Tomchik -- Wednesday, 9 November 2016, at 4:35 p.m.
  • Re: What log size is too large?
    Lester Knutsen -- Wednesday, 9 November 2016, at 4:58 p.m.
    • Re: What log size is too large?
      Fernando Nunes -- Thursday, 10 November 2016, at 5:59 a.m.
      • Re: What log size is too large?
        Fernando Nunes -- Thursday, 10 November 2016, at 6:04 a.m.
        • Re: What log size is too large?
          Art Kagel -- Thursday, 10 November 2016, at 6:31 a.m.
          • Re: What log size is too large?
            Fernando Nunes -- Thursday, 10 November 2016, at 6:40 a.m.
      • Re: What log size is too large?
        Keith Simmons -- Thursday, 10 November 2016, at 6:19 a.m.
        • Re: What log size is too large?
          Fernando Nunes -- Thursday, 10 November 2016, at 6:36 a.m.
  • Re: What log size is too large?
    Art Kagel -- Wednesday, 9 November 2016, at 5:41 p.m.
  • Re: What log size is too large?
    MARK SCRANTON -- Friday, 11 November 2016, at 5:13 p.m.

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