RE: Hot Backup Issue

[Guy Hammond]

Title: RE: Hot Backup Issue

That makes sense, I just wanted to check :0) And of course, transactions in other tablespaces would be writing redo as normal. The overall level of redo generated would surely be less, tho'? Because say you had 5 tablespaces and put them all into hotbackup mode. Then the 5th tablespace would be writing full blocks to the redo log for all the time it took to copy the datafiles of the first 4, rather than for just the time it took to copy itself if you only put tablespaces into backup mode while they were actually having their datafiles copied? And when recovering, Oracle doesn't mind that some redo information will be full blocks, and some not, if a transaction spans multiple tablespaces, one of which was in hotbackup mode and the rest not when the transaction was committed?

 

Thanks,

 

g

-----Original Message-----
From: Hallas John [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, October 02, 2001 1:45 PM
To: Multiple recipients of list ORACLE-L
Subject: RE: Hot Backup Issue

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:[EMAIL PROTECTED]]
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
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