Glenn,
My understanding is that you need to account for the time it takes to
start and complete the BCV split. The only way to do this is to put the
tablespace in hot backup mode so that you can recover the tablespace when
you bring the database up on the copied system.
If you do not do this,
Title: RE: EMC BCV Splits and Hot Backup mode.
Hi Glenn,
Are your arclogs redologs on the bcv?
Think of it in the same manner as a hot backup - what if there was a large data load going at the time of the split. There's no guarantee as to what data changes will make it on what mirror
If you lose one side of a mirrored pair, the instance doesn't notice - it just
continues to process against the survivor(s).
On the other hand, if you need to restore a backup (BCV, split mirror or
otherwise), you need to be able to roll it forward to a consistent state.
Consider a BCV split as
Question:
Why is it necessary to put the database in 'hot backup' mode when
splitting a BCV? If it is just like splitting a mirror, why do you need
the database in hot backup mode at all? Wouldn't it be the same as
losing one side of a mirrored pair? When that happens, no extra
Glenn:
If you put all the disks including your database files in one device group,
you do not have to put your source database in backup mode. Otherwise, yes,
you have to. In the first case, when you try to startup your database,
Oracle will do an 'instacne recover'.
I configured both scenaries
Well, yeah. But why is it inconsistent? Please provide details. As you are with
EMC, do you have any papers which discuss at that level? (not the process steps, I
have those. but why?)
I know that if only the datafiles are mirrored, then yes, you must use hot backup as
the redo changes
Glenn ,
even though everything are mirrored , splitting is not
instantaneous. When track or block level splitting ( I
don't know EMC uses which one. I know Hitachi uses
track level splitting ) takes place what happens to
the committed transaction which is being flushed to
that very same track or
Yes! That did it.
Now that I know splits are not instantaneous (atomic), it is perfectly clear why you
need 'hot backup' mode (to capture the complete oracle blocks).
Thanks everyone!
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Sent: Monday, September 24, 2001 6:02 PM
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