Kay, thanks for the explanation.  Sorry for being a pain in butt.  But I see 
that the C program will write IMMEDIATELY AS SOON AS the log is written.
But this is not the same as doing it simultaneously.  So there is a chance (very very
small of course) that after LGWR writes the committed transaction and before
your C program copies the block which contains the change vector that the
system crash and online redo is lost.  Therefore you can guarantee 99.99% but not 100%?
Am I correct?

Thanks again.

Richard

>>> [EMAIL PROTECTED] 11/29/01 10:45PM >>>


Richard,

Comments inline..

-----Original Message-----
Sent: Thursday, November 29, 2001 6:40 AM
To: Multiple recipients of list ORACLE-L

This sounds good, but I have a couple of questions.  How do you guarantee
that
you won't lose any committed transactions?  I mean, the C program could lag
behind
the LGWR since it's only reading it without lock and it's copying the online
redo over
to a remote machine.  So for a busy database, the LGWR will just keep
writing and the
C program won't be able to keep up with it's pace.

The external program uses X$KCCCP as a feedback for copying process. X$KCCCP
will have
the current log block (Disk RBA) and this will have the change vectors for
last commit. So you
copy the change vectors/ redo records immediately as soon as it is written.
If LGWR can keep
writing the files means why can't your C program copy the files?

Are you copying the whole partially filled online redo? or just the
difference
since the last commit?
Difference from last copy.. (last commit )



Did I miss understand it?  Please advise.

>>> [EMAIL PROTECTED] 11/29/01 12:40AM >>>

If you want to Zero data loss in standby you can copy the online redo logs
thru an external C program.  You can copy the online redo log files when
the LGWR is writing to it.

The program should read the log files without locking. You can use the fixed
table  X$KCCLE and X$KCCCP to find how much is written in the log files.
The partially filled log file  can be shipped to the standby location and
you can
open the standby database with the new control file created with NORESETLOGs
.

In this way you have a graceful fail over in the standby database and no
committed
Transaction is lost in the standby database

Does this sound good?

Best Regards,
K Gopalakrishnan
Bangalore, INDIA



-----Original Message-----
Sent: Wednesday, November 28, 2001 4:16 PM
To: Multiple recipients of list ORACLE-L

I am also facing the same problem. All these disadvantages in 8i standby DB
have been taken care of in oracle 9i version. The other solution could be to
buy an expensive Veritas Cluster server/Database edition.

Thanks,
-- Janardhana babu

-----Original Message-----
Sent: Wednesday, November 28, 2001 3:35 PM
To: Multiple recipients of list ORACLE-L


Quick question.  Is it a fair statement to say that using Oracle's hot
standby database allows you recoverability up to the last archive log, but
would NOT recover to the latest redo log (prior to a log switch).  In other
words, the potential to lose transactions is very high if you depend on this
for failover (not good for e-commerce type databases).  Would it be possible
to somehow mirror redo logs across to the failover server and apply them
when activating the standby database, or is the only real solution
clustering or something like DoubleTake?

Am I making sense?

Thanks,

Ed


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