Logical log restore
Asked whether you can restore a Day-1 level-0 archive and then apply only later days' logical logs, skipping intermediate level-0 archives and log tapes. Answer: skipping intermediate level-0 archives is fine — after restoring the Day-1 level 0, Informix prompts for the log tapes and you roll forward through Day 2 and Day 3 logs to current; but you cannot skip the Day-2 logical logs (no renumbering trick). A side discussion explained why logical logs matter (rolling a dbspace forward after a crash) and noted that with ON-Bar a single-dbspace restore must go to current, not a point in time; a whole-instance restore on a test server plus unload/reload was suggested as a workaround.
Auto-generated by DrWatson from the posts below — may be imperfect; read the full thread.
--=_F7AF59EE.ED8CE1A0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Greetings gurus, newbies, observers, spammers et al, Say I have Level 0 archives for Day 1, Day 2 and Day 3. I have logical = logs for the 3 days as well. On Day 4 is it possible to do a Level 0 = restore for Day 1 and then a logical restore for Day 2, then try to do a = logical restore for Day 3 while bypassing Level 0 for Day 2.=20 Is it also possible to do Day 1 Level 0 restore and then Day 3 logical log = restore, completely bypassing Day 2 Level 0 archive and Day 2 logical = logs. I am thinking something that would entail, maybe renumbering the log = files. hmmm... is this within the realms of possibility... Please don't ask me = the whys of it all. I am more interested in the possibilities or lack of = of a work around. TIA -kudzi --=_F7AF59EE.ED8CE1A0 Content-Type: text/plain Content-Disposition: attachment; filename="TEXT.htm" <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META content="text/html; charset=iso-8859-1" http-equiv=Content-Type> <META content="MSHTML 5.00.2919.6307" name=GENERATOR></HEAD> <BODY bgColor=#ffffff style="FONT: 10pt Arial; MARGIN-LEFT: 2px; MARGIN-TOP: 2px"> <DIV>Greetings gurus, newbies, observers, spammers et al,</DIV> <DIV> </DIV> <DIV>Say I have Level 0 archives for Day 1, Day 2 and Day 3. I have logical logs for the 3 days as well. On Day 4 is it possible to do a Level 0 restore for Day 1 and then a logical restore for Day 2, then try to do a logical restore for Day 3 while bypassing Level 0 for Day 2. </DIV> <DIV> </DIV> <DIV>Is it also possible to do Day 1 Level 0 restore and then Day 3 logical log restore, completely bypassing Day 2 Level 0 archive and Day 2 logical logs. I am thinking something that would entail, maybe renumbering the log files.</DIV> <DIV> </DIV> <DIV>hmmm... is this within the realms of possibility... Please don't ask me the whys of it all. I am more interested in the possibilities or lack of of a work around.</DIV> <DIV> </DIV> <DIV>TIA</DIV> <DIV> </DIV> <DIV>-kudzi</DIV></BODY></HTML> --=_F7AF59EE.ED8CE1A0--
What purpose do they *really* serve, anyway? We always back them up to get them out of the way, and then forget about them Or delete them). Any restores we do are always the database and programs only. Just curious... this is the same on both our AIX and RH systems. -- David Ambrose david@boarsgut.com "Kudzi Muchaka" <KMuchaka@HAFresno.org> wrote in message news:8nelqs$25l$1@news.xmission.com... > > --=_F7AF59EE.ED8CE1A0 > Content-Type: text/plain; charset=US-ASCII > Content-Transfer-Encoding: quoted-printable > Content-Disposition: inline > > Greetings gurus, newbies, observers, spammers et al, > > Say I have Level 0 archives for Day 1, Day 2 and Day 3. I have logical = > logs for the 3 days as well. On Day 4 is it possible to do a Level 0 = > restore for Day 1 and then a logical restore for Day 2, then try to do a = > logical restore for Day 3 while bypassing Level 0 for Day 2.=20 > > Is it also possible to do Day 1 Level 0 restore and then Day 3 logical log = > restore, completely bypassing Day 2 Level 0 archive and Day 2 logical = > logs. I am thinking something that would entail, maybe renumbering the log = > files. > > hmmm... is this within the realms of possibility... Please don't ask me = > the whys of it all. I am more interested in the possibilities or lack of = > of a work around. > > TIA > > -kudzi > > --=_F7AF59EE.ED8CE1A0 > Content-Type: text/plain > Content-Disposition: attachment; filename="TEXT.htm" > > <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> > <HTML><HEAD> > <META content="text/html; charset=iso-8859-1" http-equiv=Content-Type> > <META content="MSHTML 5.00.2919.6307" name=GENERATOR></HEAD> > <BODY bgColor=#ffffff > style="FONT: 10pt Arial; MARGIN-LEFT: 2px; MARGIN-TOP: 2px"> > <DIV>Greetings gurus, newbies, observers, spammers et al,</DIV> > <DIV> </DIV> > <DIV>Say I have Level 0 archives for Day 1, Day 2 and Day 3. I have logical logs > for the 3 days as well. On Day 4 is it possible to do a Level 0 restore for Day > 1 and then a logical restore for Day 2, then try to do a logical restore for Day > 3 while bypassing Level 0 for Day 2. </DIV> > <DIV> </DIV> > <DIV>Is it also possible to do Day 1 Level 0 restore and then Day 3 logical log > restore, completely bypassing Day 2 Level 0 archive and Day 2 logical logs. I am > thinking something that would entail, maybe renumbering the log files.</DIV> > <DIV> </DIV> > <DIV>hmmm... is this within the realms of possibility... Please don't ask me the > whys of it all. I am more interested in the possibilities or lack of of a work > around.</DIV> > <DIV> </DIV> > <DIV>TIA</DIV> > <DIV> </DIV> > <DIV>-kudzi</DIV></BODY></HTML> > > --=_F7AF59EE.ED8CE1A0-- >
Kudzi Muchaka wrote: > Say I have Level 0 archives for Day 1, Day 2 and Day 3. I have logical = > logs for the 3 days as well. On Day 4 is it possible to do a Level 0 = > restore for Day 1 and then a logical restore for Day 2, then try to do a = > logical restore for Day 3 while bypassing Level 0 for Day 2.=20 Absolutely. If, on Day 4, you use your Day 1 backup for the restoration, Informix will automatically prompt you for the tape containing the logical log that was current when you started the backup. You may then keep apply the Logical log tapes of Day 2 and Day 3 (you will receive prompts to them) to get to current. Alternatively, you could use you Level0 backup of Day 2 and log backups of Day 2 and 3. Or, the Level 0 backup of Day 3 and log backups of Day 3. > Is it also possible to do Day 1 Level 0 restore and then Day 3 logical log = > restore, completely bypassing Day 2 Level 0 archive and Day 2 logical = > logs. I am thinking something that would entail, maybe renumbering the log = > files. You're kidding, right? No, you can not. What you really should do is "taste the pudding". Create a small instance, modify your TAPEDEV & LTAPEDEV to disk files and fiddle around. Rudy
David Ambrose wrote:
> What purpose do they *really* serve, anyway?
Ouch! That hurt.
Have you ever had occasion to restore? Probably not.
Your Level 0 backup can be taken, as you hopefully know, while your system is
up and running - i.e in the midst of database activity. Informix ensures that
the backup is a consistent one as at the point in time that the backup started.
3 hours down the line, your system crashes. You now discover that one of the
disks has crashed and that you have to restore one of your data dbspaces.
With both onbar & ontape, you can do a selective dbspace restore using your
Level 0 backup. However, that only gets you to the point in time that the
backup had started. Now, you have to roll-forward the data in that dbspace to
get it to reflect the state at the time of the crash. This is where your
logical logs are needed. If you do not have them, you're toast.
Of course, the above assumes that your database is logged in the first place.
The ideal way to get really clear about this is to practise various scenarios
on a small test instance. On the other hand, you could wait for a real crash
and recovery to understand the importance of Logical logs :)
Rudy
In article <399BD796.E0B82288@americasm01.nt.com>, Rudy
Fernandes <rferdy@americasm01.nt.com> wrote:
> David Ambrose wrote:
> > What purpose do they *really* serve, anyway?
> Ouch! That hurt.
> Have you ever had occasion to restore? Probably not.
> Your Level 0 backup can be taken, as you hopefully
> know, while your system is
> up and running - i.e in the midst of database
> activity. Informix ensures that
> the backup is a consistent one as at the point in time
> that the backup started.
> 3 hours down the line, your system crashes. You now
> discover that one of the
> disks has crashed and that you have to restore one of
> your data dbspaces.
> With both onbar & ontape, you can do a selective
> dbspace restore using your
> Level 0 backup. However, that only gets you to the
> point in time that the
> backup had started. Now, you have to roll-forward the
> data in that dbspace to
> get it to reflect the state at the time of the crash.
> This is where your
> logical logs are needed. If you do not have them,
> you're toast.
> Of course, the above assumes that your database is
> logged in the first place.
> The ideal way to get really clear about this is to
> practise various scenarios
> on a small test instance. On the other hand, you
> could wait for a real crash
> and recovery to understand the importance of Logical
> logs :)
> Rudy
I have a level 0 backup and I just want to restore the
particular dbspace without restoring the logical logs. Hwo
can I do?
I am using onbar with Informix 8.2UD5X1 on hP-UX 11.0
I have performed as said in the manual but not succeeded.
Will you tell me how can I restore the dbspace without
restoring the logical logs?
Thanks
Sarah
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"Rudy Fernandes" <rferdy@americasm01.nt.com> wrote in message
news:399BD796.E0B82288@americasm01.nt.com...
> David Ambrose wrote:
>
> > What purpose do they *really* serve, anyway?
>
> Ouch! That hurt.
>
> Have you ever had occasion to restore? Probably not.
>
> Your Level 0 backup can be taken, as you hopefully know, while your system
is
> up and running - i.e in the midst of database activity. Informix ensures
that
> the backup is a consistent one as at the point in time that the backup
started.
>
> 3 hours down the line, your system crashes. You now discover that one of
the
> disks has crashed and that you have to restore one of your data dbspaces.
>
> With both onbar & ontape, you can do a selective dbspace restore using
your
> Level 0 backup. However, that only gets you to the point in time that the
> backup had started. Now, you have to roll-forward the data in that dbspace
to
> get it to reflect the state at the time of the crash. This is where your
> logical logs are needed. If you do not have them, you're toast.
>
> Of course, the above assumes that your database is logged in the first
place.
>
> The ideal way to get really clear about this is to practise various
scenarios
> on a small test instance. On the other hand, you could wait for a real
crash
> and recovery to understand the importance of Logical logs :)
>
> Rudy
>
>
Oic. I guess that's why whenever needed them. We take the system offline
during both our level 1's and level 0's backups. :)
Thanks for explaining.
David Ambrose
Sarah wrote:
> I have a level 0 backup and I just want to restore the
> particular dbspace without restoring the logical logs. Hwo
> can I do?
> I am using onbar with Informix 8.2UD5X1 on hP-UX 11.0
> I have performed as said in the manual but not succeeded.
> Will you tell me how can I restore the dbspace without
> restoring the logical logs?
> Thanks
> Sarah
Unless 8.2's onbar works differently from v7 & v9, you can not. dbspace restores always have to be to CURRENT. A full instance restore can be done to a
point in time, though.
The reason for this, I guess, is related to data integrity. Imagine a parent table on the dbspace you want to restore, while the children are on other
dbpsaces....
You could do the following (quite painful).
1. Restore the entire instance on a test server to the point in time you are interested in.
2. Unload the contents of the dbspace into ascii files.
3. Replace your Production instance dbspace contents with what you unloaded.
Rudy
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