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Home -> Community -> Usenet -> c.d.o.server -> Re: rollback and redo questions
A copy of this was sent to Doug Cowles <dcowles_at_bigfoot.com>
(if that email address didn't require changing)
On Tue, 10 Nov 1998 09:56:30 -0500, you wrote:
>I understand this subject much better due to your excellent postings.
>One more question. I'm just wondering about the order of redo,datafile,and
>rollback.
>In which order does this writting take place? If we are updating blocks 1-25 in
>your
>example, is this written to redo, then after the checkpoint, to the datafile and
>rollback
>simutaneously? Or is it written to redo, & rollback simutaneously, and then to the
>datafiles
>at checkpoint? Etc., Just curious.
>
redo is written pretty much continously (flushed from memory to disk) during the course of your transaction. The times it is flushed depend on a couple of things (like size of redo log buffer). It is (your redo) totally flushed upon committing of your transaction.
Rollback is stored in datafiles just like data is and rollback and 'real' data will both be written to disk whenever (in a lazy fashion in the background). Whenever might happen cause we run out of blocks in the cache and have to flush some to reclaim them, it might happen because of a checkpoint. There is no inherit order in which rollback blocks (which are data blocks really, just like index blocks are data blocks) and data blocks are written.
>Thomas Kyte wrote:
>
>> A copy of this was sent to "B.Sc Yassir Khogaly"
>> <yassir_at_khogaly.freeserve.co.uk>
>> (if that email address didn't require changing)
>> On Wed, 4 Nov 1998 15:20:50 -0000, you wrote:
>>
[snip]
>
>
Thomas Kyte
tkyte_at_us.oracle.com
Oracle Government
Herndon VA
--
http://govt.us.oracle.com/ -- downloadable utilities
Anti-Anti Spam Msg: if you want an answer emailed to you, you have to make it easy to get email to you. Any bounced email will be treated the same way i treat SPAM-- I delete it. Received on Thu Nov 12 1998 - 10:01:44 CST
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