Re: Data Guard (zero data loss)

"Timmy Sin" <tswsin_at_yahoo.com> wrote in message news:b49nof$dg3$1_at_news.hk.linkage.net...
> Is this feature practical in real life?

I doubt it. Except for environments where zero data loss isn't a highly desirable outcome but a must have.

> How about if the primary and standby
> databases are connected by a T1 WAN link?

What happens if the link goes down? Answer - your zero data loss measure becomes a zero availability measure. In order to implement zero data loss you must have a 100 per cent reliable connection to the standby(s). It is no wonder that Data Guard allows for up to 9 standby sites.

Something similar *may* happen if the standby itself fails. If you have chosen maximum protection then again you have a primary site that stops. If you chose the (somewhat misleading IMO) maximum availability option, then you get improved availability, but there now exists a possibility of data loss.

So in summary if Real Life allows for clustered primary and standby sites (peferably several of them) with redundant links between them (maybe from different providers) then yes zero loss data guard will be practical. If it doesn't....

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Niall Litchfield
Oracle DBA
Audit Commission UK