SEO

Probably a stupid question, but is there an easy way to determine how
much a table has changed since last time stats where updated? What I'm
trying to figure out is whether there is a need to do runstats on a
particular table or not.

Thanx
/Lennart

Lennart wrote:
> Probably a stupid question, but is there an easy way to determine how
> much a table has changed since last time stats where updated? What I'm
> trying to figure out is whether there is a need to do runstats on a
> particular table or not.
>
> Thanx
> /Lennart

The DB2 Health monitor tracks this, but I don't think that this is
externalized. But you could certainly leverage health monitor to
notify you when it thinks a table needs to have its statistics
updated.

Ian wrote:
> Lennart wrote:
>> Probably a stupid question, but is there an easy way to determine how
>> much a table has changed since last time stats where updated? What I'm
>> trying to figure out is whether there is a need to do runstats on a
>> particular table or not.
>>
>> Thanx
>> /Lennart
>
> The DB2 Health monitor tracks this, but I don't think that this is
> externalized. But you could certainly leverage health monitor to
> notify you when it thinks a table needs to have its statistics
> updated.
>
And in DB2 9.5 you can leave it to DB2 end to end...

Cheers
Serge

--
Serge Rielau
DB2 Solutions Development
IBM Toronto Lab

On Mar 19, 11:46 pm, Serge Rielau <srie...@ca.ibm.com> wrote:
> Ian wrote:
> > Lennart wrote:
> >> Probably a stupid question, but is there an easy way to determine how
> >> much a table has changed since last time stats where updated? What I'm
> >> trying to figure out is whether there is a need to do runstats on a
> >> particular table or not.
>
> >> Thanx
> >> /Lennart
>
> > The DB2 Health monitor tracks this, but I don't think that this is
> > externalized. But you could certainly leverage health monitor to
> > notify you when it thinks a table needs to have its statistics
> > updated.
>
> And in DB2 9.5 you can leave it to DB2 end to end...
>

Thank you Ian and Serge.



/Lennart

On Mar 19, 3:46 pm, Lennart <Erik.Lennart.Jons...@gmail.com> wrote:
> Probably a stupid question, but is there an easy way to determine how
> much a table has changed since last time stats where updated? What I'm
> trying to figure out is whether there is a need to do runstats on a
> particular table or not.
>
> Thanx
> /Lennart

The following may not work in all cases, might work best when a table
has changed a lot and has really old statistics, but might be worth a
try. If your systems are already on v9, then you should try Automatic
Runstats. I have them set to ON on my production systems and they have
been providing consistent worry-free maintenance.

Look at a plan of a recently executed SQL that accesses the table.
Above the table in question, you would see the card value for that
table. Do a select count(1)/count(*) on the table and see how much it
differs from the card value on the plan. If it differs by a lot then
the table needs runstats.

But this is only a case-by-case analysis when you are trying to fix a
bad query that now takes longer than its supposed to. I don't think
you can use this approach to prepare a regular maintenance plan. The
frequency and amount of data change in tables can only be accessed
properly by discussion with the application and data architects.

Cheers,
Sanjuro