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RE: Hot Backup Issue

From: Hallas John <John.Hallas_at_btcellnet.net>
Date: Tue, 02 Oct 2001 05:35:29 -0700
Message-ID: <F001.0039E7DF.20011002044518@fatcity.com>

Guy,
I would have thought 2) was best as you are reducing the concurrency (I think that is the right word) of redo log activity.

As each tablespace is in backup mode it writes the full block to the redo log when any changes are made. On the assumption that all tablespaces are being written (albeit infrequently) during the period of hot backup it is better to alter each tablespace, copy it then alter online again so that only 1 tablespace at a time is having full blocks of changed data writing to the redo logs.

The overall level of redo will be the same but contention (ah ha  - better word) will be reduced

John

-----Original Message-----
From: Guy Hammond [mailto:guy.hammond_at_avt.co.uk] Sent: 02 October 01 12:15
To: Multiple recipients of list ORACLE-L Subject: RE: Hot Backup Issue

Hello,

Slightly unrelated question... is it better to (in pseudo code) :

1)

for each tablespace loop
        put tablespace in backup mode

end loop

for each datafile in the database loop
        copy data file

end loop

for each tablespace loop
        put tablespace in normal mode

end loop

or 2)

for each tablespace loop
        put tablespace in backup mode
        for each datafile in this tablespace loop
                copy data file
        end loop
        put tablespace in normal mode

end loop

What I'm doing is (2), but I notice that Rajesh is doing (1). What are the pros and cons of each approach? (I'll probably use RMAN at some point, anyway :0) ).

Cheers,

g
 

-- 
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-- 
Author: Guy Hammond

  INET: guy.hammond_at_avt.co.uk
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Received on Tue Oct 02 2001 - 07:35:29 CDT

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