about logfiles

On 18 Oct 2003 04:01:54 -0700, mohan@hashprompt.com (mohanasundaram)
wrote:

>Hai,
>
> I have database with two log groups, each of this contain two
>logfiles.
> At a movement, i am delete one logfile. and now i have one log file
>which is current. In some situation this file will deleted due to some
>problem.
> Then what is the Database position ? Is it mount mode, or in
>openmode?
> plz answer me.

Hi Hai,

The DB is simply *screwed up*. And you seem quite clueless about DB
admin.
If your sentence "I have database" means "I administer a database
with data important to other than myself", stop whatever you are doing
and call a DBA!

- Kenneth Koenraadt

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
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"Howard J. Rogers" wrote in message news:<3f91a4b1$0$21651$afc38c87@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.

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.
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.

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.

Pd

Paul Drake wrote:

> "Howard J. Rogers" wrote in message
> news:<3f91a4b1$0$21651$afc38c87@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
--
--------------------------------------------
See my brand new website, soon to be full of
new articles: www.dizwell.com.
Nothing much there yet, but give it time!!
--------------------------------------------