IDS Forum

Re: WARNING Backup

Posted By: Fernando Nunes
Date: Friday, 7 September 2012, at 4:23 a.m.

In Response To: WARNING Backup (Achilleas Achilleos)

It's a long history....
Basically Informix uses the timestamp to see which pages need to be put in
a L1 or L2 backup.
Assuming the L0 was taken when the timestamp was 1000000 every page with a
timestamp bigger than this must be put in L1/L2.
But the timestamp is just a 32 bit number and can wrap around. It should
not wrap around too quickly, but let's assume you spend too much time
between L0s.
The 32 bit could wrap around and become 500000. This would mean that the
all the pages "stamped" would look older than the L0 timestamp, and as such
they would not be elected to be put in an L1/L2. This would mean a
corrupted backup.

So, much before this happens, the engine warns you that the next backup has
to be an L0.

In some cases the timestamp can jump too quickly. I remember very old bugs
(7.31) that could cause this... If your last L0 backup is not very old, you
may want to check with tech support to see if something similar may be
happening on your system.

Also note that last time I checked, the L0 would "stamp" what we would call
"very old pages", so that there is no risk of the situation above.
If you run regular L0 and if you simply don't use L1 and L2 then just
ignore the message. If you use L1 and L2 pay attention to it.
I would assume the engine would not accept to run an L1/L2 after that
message appears, but honestly I'd have to check if that happens. But some
of the backup experts can easily check this.

This issue was famous around late 7.31 and some 9.4 versions. I haven't
faced any issues with this since V10. At the time it got known as the "very
slow backup" problem, because the "very old timestamp pages stamping" was a
terribly slow process than once in a while would turn a 1H backup into a
7/8H ones...

Regards.

On Fri, Sep 7, 2012 at 6:04 AM, Achilleas Achilleos <
AchilleasAchilleos@semltd.com.cy> wrote:

> Hi to ALL
>
> Hi to ALL
>
> In our company we are using "IBM Informix Dynamic Server Version 11.50.FC3"
>
> on AIX platform "6.1.0.0"
>
> The last few days I get a WARNING in the message log to perform a Level 0
> backup.
>
> 12:20:32 WARNING: Next backup of DBspace aabbdbs must be level-0 backup.
>
> 12:20:32 WARNING: Next backup of DBspace bbccdbs must be level-0 backup.
>
> 12:20:32 WARNING: Next backup of DBspace ccdddbs must be level-0 backup.
>
> 12:20:32 WARNING: Next backup of DBspace ddeedbs must be level-0 backup
>
> Why is this happening ?????
>
> Regards
>
> Description: Description: CoopLogo1Description: Description: CoopLogo1
>
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>
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>
> Official A
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>
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>
>
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> *******************************************************************************
> Forum Note: Use "Reply" to post a response in the discussion forum.
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>

--
Fernando Nunes
Portugal

http://informix-technology.blogspot.com
My email works... but I don't check it frequently...

--00235452f64ced5f3604c91853e9

Messages In This Thread

• WARNING Backup
  Achilleas Achilleos -- Friday, 7 September 2012, at 1:04 a.m.
  • Re: WARNING Backup
    Fernando Nunes -- Friday, 7 September 2012, at 4:23 a.m.
    • Re: WARNING Backup
      Art Kagel -- Friday, 7 September 2012, at 6:17 a.m.
      • Re: WARNING Backup
        Fernando Nunes -- Saturday, 8 September 2012, at 4:14 a.m.
        • Re: WARNING Backup
          John Miller iii -- Saturday, 8 September 2012, at 11:04 a.m.
          • Re: WARNING Backup
            Fernando Nunes -- Saturday, 8 September 2012, at 12:51 p.m.
  • Re: WARNING Backup
    Art Kagel -- Friday, 7 September 2012, at 6:10 a.m.

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