Informix

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  • 1.  sbspace defaults

    Posted 30 days ago
    Informix 12.10.FC14
    Solaris 10  1/13

    Q1: When one uses onspaces -ch to change a default value (for example to turn logging off), does one need to include all the values that were originally set (in addition to the value one wishes to change)?  That is, would specifying just the value one wants to change cause Informix to revert any other (modified) default values to revert to the system default values?

    Also, I created a new sbspace and specified AVG_LO_SIZE = 27 in the onspaces command.  I have not yet put anything in that newly created space.  Now, when I run 'onstat -g smb s', I get:



    informix@ifmx-prod-jnu>onstat -g smb s

    IBM Informix Dynamic Server Version 12.10.FC14 -- On-Line -- Up 13 days 07:39:49 -- 14974976 Kbytes

    Sbspace Summary:

    sbnum 11 address 11b245c20
    Space       :  flags        nchk       owner           sbname
                        --------      1            informix         acoms1_sblb
    Defaults    : LO_LOG

    LO            : ud b/pg     flags       flags             avg s/kb        max lcks
                      2048         0              --------         26                  -1
    Ext/IO       : 1st sz/p     nxt sz/p    min sz/p      mx io sz
                      0                0             0                 -1

    HdrCache : max          free
                       512          0


    Q2: Why does 'onstat -g smb s' show 26 for the avg size, when I specified 27 in the onspaces -c command that created the space?


    Thank you for any comments.

    Regards,

    DG

    ------------------------------
    David Grove
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  • 2.  RE: sbspace defaults

    Posted 30 days ago
    While walking to work, this morning, a possible answer to Q2 popped into my head.

    I'm thinking that, since the blob pages are built from regular Informix pages (I guess I am just assuming this), I should specify an AVG_LO_SIZE that is an integer number of pages (which, in my case, is 2K).  Thus, I should have specified either 26 or 28 for AVG_LO_SIZE.  Informix likely used the closest value to what I specified that is an integer number of pages and does not exceed the value I specified.

    That's my story, and I'm sticking to it.

    (Unless I turn out to be wrong.)

    DG

    ------------------------------
    David Grove
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  • 3.  RE: sbspace defaults

    InnerCircle
    Posted 29 days ago
    Hi David,

    answer to Q1 is no, only those characteristics specified in your command will be modified, and only if specified values differ from existing ones.

    For Q2, you guessed correctly, any average LO size specified would be rounded down to next lower multiple of base page size, to be on safer side with calculating the space set aside for metadata ('meta data area') - which actually is the only point in specifying such avg. LO size.
    What is not quite correct is your assumption of 'blob pages': as opposed to blobspaces, there's no such thing as blob pages in an sbspace, only extents of regular pages which actual sblobs are made up from.

    HTH,
     Andreas

    ------------------------------
    Andreas Legner
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  • 4.  RE: sbspace defaults

    Posted 28 days ago
    Thank you for your helpful reply.

    And for setting me straight on (the non-existence of) blobpages in sbspaces.

    DG

    ------------------------------
    David Grove
    ------------------------------