Re: hotbackup: cp clonefile versus alter database backup controlfile
- From: Tanel Põder <tanel.poder.003@xxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Tue, 3 Aug 2004 19:25:40 +0300
> I have used "diff" on unix to compare the control files from "cp" method
and
> "ALTER DATABASE BACKUP CONTROLFILE TO" and found they were different (BTW,
> no database structure changes were made during this whole process).
Starting from 8i, the incremental checkpoint feature makes CKPT process to
update controlfile every 3 seconds anyway (in addition to possible redolog
record updates during logswitch and updates during full checkpoint etc).
> I am curious and would like to know: In what situation "cp controlfile"
> method would prevent me from doing a "COMPLETE RECOVERY"? Would a db
> structure change (during hot backup) make "cp controlfile" method not
> working?
In the situation where Oracle simply says that your controlfile is corrupt
and it can't open it.
Btw, Oracle controlfiles store old-images of the blocks in them for crash
recovery, that way they survive from regular instance failures, but I
definitely don't recommend backing up a mounted controlfile by OS utilities
(a complete atomic snapshot of the whole database being a rare exception).
Tanel.
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