Re: CDC using LogMiner in RAC environment

I found a note in the 11g doc that is not in the 10g doc set that is
pertinent to our situation:

"You should only use CONTINUOUS_MINE on an Oracle RAC database if no
thread is being enabled or disabled."

Looking more like CDC based on LogMiner in a RAC environment is not
going to function that reliably.

Thanks,
Jeff


On Mon, Sep 29, 2008 at 11:14 AM, Jeffery Thomas <jeffthomas24@xxxxxxxxx> wrote:
> Currently, we are using an Informatica product to perform CDC  in a
> 10.2.0.4, two-node RAC environment.
> The product has a listener that receives results from an ad-hoc query
> against V$LOGMNR_CONTENTS in
> continuous mining mode, then ships relevant transactions to a
> different database.
>
> The process seems  somewhat fragile.  If we take down one instance for
> maintenance (or if it crashes) the
> LogMiner session ends due to the disabled thread.   A mining session
> can also sporadically terminate as a
> result of a hot  backup,  apparently due to the alter system archive
> log issued by RMAN.    There is a known
> bug in 10.2.0.4 RAC (fixed in 11.2) where a LogMiner continuous mining
> session terminates due to a disabled
> thread that we are discussing with Support.
>
> There's no filtering of redo by the ad-hoc query, the SELECT has no
> WHERE.  The business logic is outside
> the database in the Informatica piece so that all redo records mined
> are forwarded to the external 3rd-party
> listener.  So in a busy source database there can be a considerable
> lag between the  time of the commit of a
> relevant transaction to when it gets shipped to the target database.
>
> My question(s) would be:  is LogMiner alone onsidered sufficiently
> robust and reliable to provide near real-time CDC?
> Is it intended to be used in that fashion where the usage is simply an
> un-filtered ad-hoc select against
> V$LOGMNR_CONTENTS in continuous mining mode and shipping the data
> outside to an external 3rd-party
> tool?
>
> Reading about LogMiner in the  Oracle docs does not mention CDC per
> se, only identifying it as a tool for auditing
> and data analysis.    If we were to use Streams which seems to be the
> recommended Oracle CDC mechanism and
> that also uses LogMiner under the hood, would we see the same
> fundamental issues as we are currently
> experiencing?
>
> Thanks,
> Jeff
>
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