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Re: Any Data Guard gotchas?

From: Erik Dahle <erik.dahle_at_gmail.com>
Date: 6 Feb 2006 11:04:29 -0800
Message-ID: <1139252669.090409.108990@g47g2000cwa.googlegroups.com>


Dusan Bolek skrev:
> We had and sometimes are still having some issues with 9i R2 Data
> Guard. One of the most annoying is the the fact that in the MAXIMIZE
> AVAILABILITY mode a database is not checking if there are any archived
> logs available and is crashing if there is any gap (even fetchable from
> archived logs). That means that in most of the cases, restarted Data
> Guard primary site will not start and the protection mode must be
> changed to MAX PERFORMANCE to synchronize everything and then back. Why
> in most of the cases Data Guard stanby got desynchronized even if
> shutdown was done properly (i.e. shutdown immediate on primary and
> cancel recovery + shutdown on standby) we have never learned.
> Also some issues with RMAN, such as impossibility of using old RMAN
> catalog after failover, are unconvenient.
> Data Guard is also not reporting gaps consistently, so for DG it is
> possible to become desynchronized with only one (not repeated) message
> in the alert log, which could be easily overlooked. It is even worse,
> because data dictionary view V$ARCHIVE_GAP may or may not report gaps
> correctly (was verified by Oracle Support).
> Overall impression from our Data Guard is that we are migrating to SRDF
> in few months and no one will be missing DG when it will be gone.

I guess this should answer some of your questions: Fetch Archive Log (FAL) - The FAL process has two components: FAL Client and FAL Server. Both processes are used for archive gap resolution. If the Managed Recovery Process (MRP) on the RAC Grid site detects an archive gap sequence, it initiates a fetch request to the FAL client on the standby site. This action, in turn, requests the FAL server process on the primary database to re-transmit the archived log files to resolve the gap sequence. Archive gap sequences will be discussed later in this chapter.
Check this URL for details:
http://www.oracle-base.com/articles/9i/DataGuard.php

--
Erik
Received on Mon Feb 06 2006 - 13:04:29 CST

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