Re: Slow running jobs

Russ,

The same cursor can easily vary in time when bind variables change. The bind variable might be going into an index, which then results in a read from disk for each record matching the bind variable. The number of records matching the bind variable will affect the query time. For example (pretend of course):

I have a table of bank account balances, with 50 entries in January, 10 entries in February and 300 entries in March. I have an index on month. When I say "select sum(how_rich_am_i) from my_bank_account where month = :b1" and b1 is Feb then 50 records must be located and aggregated, when b1 is Mar then 300 records must be located and aggregated.

Unfortunaltely this is indicative of normal behaviour. Of course if the query takes a different time with the same bind variable values then it most likely indicates either a caching side-effect or some other load on the machine besides your query.

Regards,

     Mark.

                                                                                                                   
                    "Brooks, Russ"                                                                                 
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                    root_at_fatcity.c                                                                                 
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                    12/03/2003                                                                                     
                    03:34                                                                                          
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Hi,
  We're having slow response on some batch jobs in our production system. A straight SQL trace shows intermittant slow response times on selects against a variety of tables. What is odd is:

1. the statistics are current for the tables, frequently the results of a compute.
2. The same cursor with different bind variables will randomly vary from 200 microseconds to 3.6 seconds, randomly.
3. This occurs on multiple tables in multiple tablespaces. What is this normally indicative of?

The other thing I did was run a 10046 level 8 trace for about 20 seconds. I saw 22 log file sync's in that period in the trace file.

Any thoughts welcome.

Russ

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