LBU_PRESERVE error message

LBU_PRESERVE error message

Post by Manel Falcó i Ai » Sun, 31 Dec 1899 09:00:00



Hi,
If I do oncheck -pr I can see this error message within:

...
    LBU_PRESERVE                   0                    
ONCONFIG config file error on element LBU_PRESERVE.    
    Value in reserved page:  0                          
    Value in config file:    1                          
...

But I put "Y" some times ago, mayby by editing onconfig file directly.
Is that the reason ? Why aren't both synchronized yet ?
Which is the right  one ???

BTW,  what happens in a long transaction with LBU_PRESERVE and what
can I do in order to make it carry on ? by adding more logs in that
moment ? is that possible ?

Another thing. I configured logs of 500 size but the output shows of
250 size. Why ?

Ok, Thanks a lot,
Manel Falc

 
 
 

LBU_PRESERVE error message

Post by Panka » Sun, 31 Dec 1899 09:00:00



Quote:>Hi,
>If I do oncheck -pr I can see this error message within:

>...
>    LBU_PRESERVE                   0
>ONCONFIG config file error on element LBU_PRESERVE.
>    Value in reserved page:  0
>    Value in config file:    1
>...

>But I put "Y" some times ago, mayby by editing onconfig file directly.
>Is that the reason ? Why aren't both synchronized yet ?
>Which is the right  one ???

The one that is right is value in the Reserved Page. You need to bounce the
Informix Instance for the change in the onconfig file to take effect.

Quote:

>BTW,  what happens in a long transaction with LBU_PRESERVE and what
>can I do in order to make it carry on ?
> by adding more logs in that
>moment ? is that possible ?
>Another thing. I configured logs of 500 size but the output shows of
>250 size. Why ?

The output of onstat -l is in pages so that is why you see 250. i.e Multiple
by  2K.
Quote:

>Ok, Thanks a lot,
>Manel Falc


 
 
 

LBU_PRESERVE error message

Post by Art S. Kage » Sun, 31 Dec 1899 09:00:00



Quote:

> Hi,
> If I do oncheck -pr I can see this error message within:

> ...
>     LBU_PRESERVE                   0
> ONCONFIG config file error on element LBU_PRESERVE.
>     Value in reserved page:  0
>     Value in config file:    1
> ...

> But I put "Y" some times ago, mayby by editing onconfig file directly.
> Is that the reason ? Why aren't both synchronized yet ?
> Which is the right  one ???

Changes to the onconfig file ONLY take place when the server is
bounced with the sole exception of the TAPE* parameters and, IFF the
change is made using onmonitor instead of an editor, the LTAPE*
parameters.

Quote:> BTW,  what happens in a long transaction with LBU_PRESERVE and what

Same thing that happens without it except that there will always be
one full logical log file empty if a long transaction rollback fills
all of the logs trying to rollback.  Then you can shutdown, change
LBU_PRESERVE to 0 and have a reasonable expectation that there will
be enough logspace in that one remaining log to complete the rollback
during fast recovery.

Quote:> can I do in order to make it carry on ? by adding more logs in that
> moment ? is that possible ?

No.

Quote:> Another thing. I configured logs of 500 size but the output shows of
> 250 size. Why ?

Onstat shows pages but onparams and the ONCONFIG file requires KB so
onstat will always show 1/2 or 1/4 depending on your platform.

Art S. Kagel

 
 
 

LBU_PRESERVE error message

Post by Manel Falcó i Ai » Sun, 31 Dec 1899 09:00:00


Thanks Art, only one doubt  as usual ...

Quote:>Changes to the onconfig file ONLY take place when the server is
>bounced with the sole exception of the TAPE* parameters and, IFF the
>change is made using onmonitor instead of an editor, the LTAPE*
>parameters.

Well, I think I changed it via onconfig file, but I said then to my
customer to shutdown after finishing working that day ... and he did

Quote:

>Same thing that happens without it except that there will always be
>one full logical log file empty if a long transaction rollback fills
>all of the logs trying to rollback.  Then ***you can shutdown***, change
>LBU_PRESERVE to 0 and have a reasonable expectation that there will
>be enough logspace in that one remaining log to complete the rollback
>during fast recovery.

When fails, it tries to rollback but if it cannot ... what happens
with the transaction. Which is its state  ? shall it commit it the
rest ?
So, when you say  "you can shutdown" is immediately after the fail
occurs ?? if not, what happens if you shutdown after a while ?  can
users go on ?

Quote:

>> can I do in order to make it carry on ? by adding more logs in that
>> moment ? is that possible ?

>No
Would be good

 
 
 

LBU_PRESERVE error message

Post by Art S. Kage » Sun, 31 Dec 1899 09:00:00



Quote:

> Thanks Art, only one doubt  as usual ...

> >Changes to the onconfig file ONLY take place when the server is
> >bounced with the sole exception of the TAPE* parameters and, IFF the
> >change is made using onmonitor instead of an editor, the LTAPE*
> >parameters.

> Well, I think I changed it via onconfig file, but I said then to my
> customer to shutdown after finishing working that day ... and he did

Then it should have taken effect.

Quote:> >Same thing that happens without it except that there will always be
> >one full logical log file empty if a long transaction rollback fills
> >all of the logs trying to rollback.  Then ***you can shutdown***, change
> >LBU_PRESERVE to 0 and have a reasonable expectation that there will
> >be enough logspace in that one remaining log to complete the rollback
> >during fast recovery.

> When fails, it tries to rollback but if it cannot ... what happens
> with the transaction. Which is its state  ? shall it commit it the
> rest ?

When a long transaction begins to rollback there is no other immediate
effect.  After a while the rollback records and other transactions may
cause the logs to reach the LTXEHWM which will halt all other
transactions in an attempt to reserve the remaining log space for the
rollback of this long transaction.  At this point no update processing
is occurring for ANY other thread.  If the logs fill to the point
where there is no space for any more rollback records in backed up
logical logs, or except for one if LBU_PRESERVE is set to 1, then
the engine will hang waiting for you to backup the logical logs.  In
general this cannot be done because there is no room in the logs for
the checkpoint and begin archive records to be written either so the
engine is hung for updates.  Soon the next checkpoint period will
occur and that will block readers also until the checkpoint record
can be written and it cannot since there is no room so the engine
goes into CHKPT REQ mode and hangs altogether.  At this point if you
have set LBU_PRESERVE you can run onmode -ky and shutdown the engine
then clear LBU_PRESERVE to release the last logical log for reuse,
and restart the engine to single user mode so you will have a chance
to complete Fast Recovery and complete the pending rollbacks and
then backup the logical logs.  If you have NOT set LBU_PRESERVE you
are hosed and have to call tech support to truncate the last logical
log or two on disk to allow the rollbacks.  In this case some
committed transactions MAY be lost or rolled back due to the
truncation but this is unlikely unless you have the LTX parameters
set way too low.

Quote:> So, when you say  "you can shutdown" is immediately after the fail
> occurs ?? if not, what happens if you shutdown after a while ?  can
> users go on ?

See above.

Quote:

> >> can I do in order to make it carry on ? by adding more logs in that
> >> moment ? is that possible ?

> >No
> Would be good

Unfortunately it's a catch 22.  To add logical logs you have to a) log
that fact, b) create a level 0 archive to enable the new logs.  
Unfortunately there is no logical log space free, in this case, to
enable you to perform these two tasks so...

Art S. Kagel

 
 
 

1. TBLSPACE_STAT / LBU_PRESERVE

Hi Users,

I am working on Sun Solaris 2.51 / IDS 7.3. Have some queries for which have
not found answers in Informix Answers Online :

1. TBLSPACE_STAT set to 1 in ONCONFIG .... what is its use.

2. We use continous backup , so do we need to set LBU_PRESERVE TO 1. How
does this parameter really help. It only avoids a dead-lock , but how does
the DBA know that all but 1 logs are full ????

3. We have a EMC 18 GB disk rack with 18 GB for mirror. We have a 2 GB chunk
for tmpdbs to do our DW queries. Would we have a performance improvement if
we spread out the temporary database to 2-3 X 2GB  tmpdbs(1,2,3) ???

Thanks in advance for Ur responses...

Prashant

______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com

2. Problem with database

3. LBU_PRESERVE

4. Informix and ChiliSoft

5. LBU_PRESERVE and LTXHWM

6. getting cursor metadata

7. How to use LBU_PRESERVE

8. Selects from recordsets?

9. Help:Record/Key Deleted message and Error message Numbers

10. getting message description using message error code..

11. oninit -i: "Cannot find message file"- Error Messages

12. Read error messages from message-area

13. Getting the full error message, not just @@ERROR.