Overwritten Logical Volume Block in AIX?

Overwritten Logical Volume Block in AIX?

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



We are running AIX 4.3.3 and Informix Dynamic Server Version 7.31.UC3. I am
wondering if Informix writes any information over the AIX logical volume
control block (LVCB) at the first 512 bytes of each logical volume. When I run
the command "onstat -pP 1 0" I see the following:
******************************************************************
carsi: oncheck -pP 1 0                                                    
addr     stamp        nslots    flag type                 frptr frcnt next    
prev      
100000   1273408739 1      1000   ROOTRSV      124   3964  0        0      
        slot ptr   len   flg                                              
        1    24    108   0                                                
slot   1:                                                                
    0: 49 4e 46 4f 52 4d 49 58 2d 4f 6e 4c 69 6e 65 20     INFORMIX-OnLine  
   16: 43 6f 70 79 72 69 67 68 74 28 43 29 20 31 39 38   Copyright(C) 198
   32: 36 2c 20 31 39 38 37 20 20 49 6e 66 6f 72 6d 69   6, 1987  Informi
   48: 78 20 53 6f 66 74 77 61 72 65 2c 20 49 6e 63 2e   x Software, Inc.
   64:  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0            
................
   80:  0  0  0  0 10  0  0  0 33 ba 5a a4  0  0  0  6          
........3:Z$....
   96:  0  0  0  0  0  0  0  0 37 2e 33 30                          
........7.30....
**************************************************************************
**********
This looks to me like at least some of the LVCB was overwritten by Informix, if
this slot exists at the beginning of the logical volume. I am coming from a
Unix admin perspective and don't know much (yet) about Informix so appreciate
any info. Thanks. CKG
 
 
 

Overwritten Logical Volume Block in AIX?

Post by Madison Prue » Sun, 31 Dec 1899 09:00:00


If you are using AIX's logical volumn manager, I think that you need to use an
offset
for the start of the chunk. It's been a while since I've looked at this, but I
think that
on AIX if you do not do this, then the first set of pages will be overwritten by
AIX
when the system is next booted.

> We are running AIX 4.3.3 and Informix Dynamic Server Version 7.31.UC3. I am
> wondering if Informix writes any information over the AIX logical volume
> control block (LVCB) at the first 512 bytes of each logical volume. When I run
> the command "onstat -pP 1 0" I see the following:
> ******************************************************************
> carsi: oncheck -pP 1 0
> addr     stamp        nslots    flag type                 frptr frcnt next
> prev
> 100000   1273408739 1      1000   ROOTRSV      124   3964  0        0
>         slot ptr   len   flg
>         1    24    108   0
> slot   1:
>     0: 49 4e 46 4f 52 4d 49 58 2d 4f 6e 4c 69 6e 65 20     INFORMIX-OnLine
>    16: 43 6f 70 79 72 69 67 68 74 28 43 29 20 31 39 38   Copyright(C) 198
>    32: 36 2c 20 31 39 38 37 20 20 49 6e 66 6f 72 6d 69   6, 1987  Informi
>    48: 78 20 53 6f 66 74 77 61 72 65 2c 20 49 6e 63 2e   x Software, Inc.
>    64:  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
> ................
>    80:  0  0  0  0 10  0  0  0 33 ba 5a a4  0  0  0  6
> ........3:Z$....
>    96:  0  0  0  0  0  0  0  0 37 2e 33 30
> ........7.30....
> **************************************************************************
> **********
> This looks to me like at least some of the LVCB was overwritten by Informix, if
> this slot exists at the beginning of the logical volume. I am coming from a
> Unix admin perspective and don't know much (yet) about Informix so appreciate
> any info. Thanks. CKG


 
 
 

Overwritten Logical Volume Block in AIX?

Post by Helmut Leininge » Sun, 31 Dec 1899 09:00:00



> If you are using AIX's logical volumn manager, I think that you need to use an
> offset
> for the start of the chunk. It's been a while since I've looked at this, but I
> think that
> on AIX if you do not do this, then the first set of pages will be overwritten by
> AIX
> when the system is next booted.


> > We are running AIX 4.3.3 and Informix Dynamic Server Version 7.31.UC3. I am
> > wondering if Informix writes any information over the AIX logical volume
> > control block (LVCB) at the first 512 bytes of each logical volume. When I run
> > the command "onstat -pP 1 0" I see the following:
> > ******************************************************************
> > carsi: oncheck -pP 1 0
> > addr     stamp        nslots    flag type                 frptr frcnt next
> > prev
> > 100000   1273408739 1      1000   ROOTRSV      124   3964  0        0
> >         slot ptr   len   flg
> >         1    24    108   0
> > slot   1:
> >     0: 49 4e 46 4f 52 4d 49 58 2d 4f 6e 4c 69 6e 65 20     INFORMIX-OnLine
> >    16: 43 6f 70 79 72 69 67 68 74 28 43 29 20 31 39 38   Copyright(C) 198
> >    32: 36 2c 20 31 39 38 37 20 20 49 6e 66 6f 72 6d 69   6, 1987  Informi
> >    48: 78 20 53 6f 66 74 77 61 72 65 2c 20 49 6e 63 2e   x Software, Inc.
> >    64:  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
> > ................
> >    80:  0  0  0  0 10  0  0  0 33 ba 5a a4  0  0  0  6
> > ........3:Z$....
> >    96:  0  0  0  0  0  0  0  0 37 2e 33 30
> > ........7.30....
> > **************************************************************************
> > **********
> > This looks to me like at least some of the LVCB was overwritten by Informix, if
> > this slot exists at the beginning of the logical volume. I am coming from a
> > Unix admin perspective and don't know much (yet) about Informix so appreciate
> > any info. Thanks. CKG

Hi,

Honda75:
Yes, you are right, Informix overwrites the LVCB if you do not specify an offset for
your chunk/dbspace. Therefor it is good usage to specify an offset of 1 page (4k).

Madison Pruet:

No, AIX does *not* overwrite the "destroyed" LVCB during reboot. AIX checks for a
valid LVCB, if its overwritten it does not recreate it. The only consequence is that
some LV-Informations are lost and cannot be used by LVM.

Regards
--
Helmut Leininger

Bull AG / Vienna
Open Systems Support



This opinion is mine and not necessarily that of my employer.
No guarantees whatsoever.

 
 
 

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