IDS Forum

Re: HDR

Posted By: Art Kagel
Date: Thursday, 13 August 2009, at 10:18 a.m.

In Response To: HDR (ANDREW PISTOCCHI)

See responses below:

Art

Art S. Kagel
Oninit (www.oninit.com)
IIUG Board of Directors (art@iiug.org)

Disclaimer: Please keep in mind that my own opinions are my own opinions and
do not reflect on my employer, Oninit, the IIUG, nor any other organization
with which I am associated either explicitly or implicitly. 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, Aug 13, 2009 at 9:46 AM, ANDREW PISTOCCHI <APISTOCCHI@ut.edu> wrote:

> I'm getting ready to turn on HDR between our production site and our D/R
> site located 7 miles away. We are running Jenzabar CX on Informix 10
> and HPUX 11i v2. Our 2 servers are connected via a 20 MB pipe. I've
> gone through the documentation but I have some questions below. We have
> a very busy system so I'm trying to avoid little downtime on our
> production site.
>
> 1. We don't want our DR server to take over automatically in any
> case. If we have a planned shutdown of production, I want to manually
> get the D/R site ready. Would I set the DRAUTO parameter in the
> ONCONFIG file to 0 - Manual? And do I do this on the primary server
> only?

No, do this on both servers.

>
>
> 2. Are there any other settings in the ONCONFIG file I need to
> change? I've seen other DR parameters in the documentation, i.e.
> DRIDXAUTO, DRINTERVAL, etc. And again, just on the primary server?

Yes, you should configure these parameters as well unless you are OK with
the defaults.

>
>
> 3. Can I use ontape -r? This is what I've been using for a full
> restore on my D/R box. When beginning replication, the documentation
> says to use ontape -p? Just curious what the difference is between the
> two.

Use ontape -p. The difference is that ontape -r also restores the logical
logs or tells the engine that there are no logical logs to restore. The
ontape -p does not restore local logical logs and leaves the engine waiting
for the primary to start shipping over its logical logs. All of the logs
since the time the archive was take must be on disk (ie not yet overwritten)
on the primary in order for the secondary server initialization to succeed.

>
>
> 4. From most of the readings, I would think I would be using
> asynchronous communication, correct? Is this also defined on just the
> primary? What is the difference between the synchronous and
> asynchronous communication?

Define it on both in case you decide after a primary crash to make the
recovered primary the secondary for a time until you can find a maintenance
window to reverse them again. You use synchronous if you are using the
secondary actively for queries that must return the exact data as the
primary as soon as possible and if it is critical that the secondary be in
exact synch with the primary. In asynch mode there is a possibility that a
transaction committed on the primary will not have been transmitted to the
secondary before the primary crashed and so they will be out-of-synch when
the secondary takes over as primary. That last transaction(s) will be lost
when you have to restore the primary from the secondary because they are not
in synch and a catchup is no longer possible.

>
>
> 5. Once I have replication going, there may be times where I need
> to do maintenance on one or both of the servers. What would be the
> process for stopping HDR on both servers but keeping my production
> engine up and running? I want to develop a good procedure, if I'm out
> of town or not available and for whatever reason, a backup admin needs
> to turn HDR off but keep production running. My main concern is there a
> need to stop the Informix engine on production?

To your last: sometimes. If you have to do maintenance on the machines,
you'll stop replication and restore it afterwards. If you have to do
maintenance on the servers themselves, it will depend on what you are
doing. Some things can be done with HDR online, others cannot.

>
>
> 6. Finally, let's just say I had HDR turned off for several hours
> and I'm ready to turn on again. Do I need to go through the steps again
> including the full tape restore or can it pickup by starting HDR again?

As long as the last logical log that the secondary knows about is still
available on disk on the primary, then you will not have to perform a
restore again, the primary will ship over the logs that the secondary missed
when you reestablish HDR. If that oldest log has been overwritten on the
primary already, then yes you have to restore again. You should have enough
logical logs on an HDR server to allow the server to be offline for any
reasonable maintenance or quickly fixed hardware failure without overwriting
the logs. Say 24 to 96 hours depending on your uptime and recovery
requirements.

>
>
> My boss is pressuring me to get this working since we are in hurricane
> season. Right now, my plan is to run a complete restore using HP's
> Ignite for the file system and then restore the Informix database from
> tape. This works but is a timely process. Any help would be
> appreciated. Thanks.
>
> Andy Pistocchi
>
> DBA / Systems Administrator
>
> The University of Tampa
>
> 813-257-3196
>
>
>
> *******************************************************************************
> Forum Note: Use "Reply" to post a response in the discussion forum.
>
>

--001636c5acf8b7e1fb0471069ba2

Messages In This Thread

• HDR
  ANDREW PISTOCCHI -- Thursday, 13 August 2009, at 9:46 a.m.
  • Re: HDR
    Art Kagel -- Thursday, 13 August 2009, at 10:18 a.m.
    • RE: HDR
      mosserp@wellsfargo.com -- Friday, 14 August 2009, at 1:57 p.m.
      • RE: HDR
        Madison Pruet -- Friday, 14 August 2009, at 4:35 p.m.
      • Re: RE: HDR
        PETER LANE -- Tuesday, 18 August 2009, at 12:40 p.m.
        • RE: HDR
          mosserp@wellsfargo.com -- Tuesday, 18 August 2009, at 2:07 p.m.
  • Re: HDR
    Madison Pruet -- Thursday, 13 August 2009, at 10:20 a.m.

IDS Forum is maintained by Administrator with WebBBS 5.12.