Re: about logfiles

From: Howard J. Rogers <hjr_at_dizwell.com>
Date: Mon, 20 Oct 2003 05:58:26 +1000
Message-Id: <3f92ed69$0$28121$afc38c87@news.optusnet.com.au>

Paul Drake wrote:

> "Howard J. Rogers" <hjr_at_dizwell.com> wrote in message
> news:<3f91a4b1$0$21651$afc38c87_at_news.optusnet.com.au>...

>> mohanasundaram wrote:
>>
>> > Hai,
>> >
>> > I have database with two log groups, each of this contain two
>> > logfiles.
>>
>>
>> We refer to those two files as MEMBERS of the log group.
>>
>> > At a movement, i am delete one logfile.
>>
>> Please don't. Deleting log files means (potentially) lost data. On the
>> other hand, I'm not clear whether you are talking about deleting one of
>> your log groups, or deleting one of the members from one of your log
>> groups.
>>
>> >and now i have one log file
>> > which is current.
>>
>> If you had two log groups, and you entirely get rid of one of those
>> groups, then your database will be stuffed, although you might not have
>> actually lost any data yet.
>>
>> >In some situation this file will deleted due to some
>> > problem.
>>
>> If you now drop the other group, especially if it is the current log
>> group, then you have definitely just lost data.
>>
>> > Then what is the Database position ? Is it mount mode, or in
>> > openmode?
>>
>> You will not be able to get a database open if the controlfile thinks it
>> has two working redo log groups, and you've arranged for there to be just
>> one, or even none. If you try a 'startup' command, you will fall over
>> into the mount state (ie, the controlfile can be read correctly, but
>> something about the data files and redo logs prevents the database going
>> on into the fully open state).
>>
>> If, on the other hand, you delete MEMBERS from log groups, that will not
>> prevent the database from being opened. Provided the control file can
>> find one working member from each group, the database can be opened.
>> That's why, of course, you are strongly recommend to have "multiplexed"
>> redo logs in the first place (ie, groups with more than one member) so
>> that you have some resilience and redundancy. A member can disappear, and
>> the database will continue to work normally. But if an entire group
>> disappaears, your database will crash, be unable to be re-opened, and you
>> may well have lost committed data.
>>
>> > plz answer me.
>>
>> Be precise in the terminology you use. Groups and members. And then the
>> answers will be clearer for you.
>>
>> Regards
>> HJR

> 
> Its been awhile since I tried it, but I don't believe that oracle will
> allow for there to be less than 2 redo log groups.

Of course it doesn't.

But what happens if you run off to the O/S and say "rm *.log"?? The original poster made no claims about whether he'd *dropped* a log group/member or whether he'd *deleted* it.

> 
> A redo log switch with only one group? Sounds like one hand clapping,
> to me.
> 
> It then follows that he was not able to remove one of only 2 log
> groups.

Does it really? Quite what "At a movement I delete on log file" actually means, it's hard to know, precisely. But I was rather under the impression that "rm *.log" was a delete. As was "delete *.log".

Point is Paul, it doesn't "follow".

> I would have to think that he removed a member of a redo log group.
> 
> His original post lacked enough info in an intelligible format to be
> considered to be worthy of replying to.

Well, don't reply to him then!!!

Why in heaven's name you nevertheless take the trouble to make a post in reply to one of mine about the lameness of my deductions because it "follows" the guy could only have been doing one thing, I have no idea. But if you don't consider the original poster "worthy" of a reply, just don't reply.  

> The only advice I would have for him was to restore the affected files
> from the cold backup that he made prior to even thinking about
> removing redo log members.

Oh, so you do now have some advice. Why not flesh it out a little?

Othrwise *your* post comes across as mere carping.

HJR

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Received on Sun Oct 19 2003 - 14:58:26 CDT