Performance Tool Question (CONFIO DBFlash ) ...

I have been reviewing the white papers for the DBFlash product from CONFIO. I am impressed, but I do have one reservation.  

DBFlash works by running a SQL statement (or group of statements) against X$ tables on the monitored database once every second. The data is pulled across the network to a repository on a separate database server and database instance and analyzed. A gui client can then access the repository and tell you which SQL statements are waiting the most, and what wait events the SQL statements are waiting on. It can also do this for database users, OS users, programs, and a few more.  

My concern has to do with the frequency of polling (once every second). Oracle records waits in micro seconds, there are 1 million micro-seconds in a second (I think). So a wait can last 10,000 microseconds, and not be picked up by the software. In fact, I would think that most waits would not be picked up by the software because most waits probably start after one snapshot and finish before the start of the next snapshot.  

I posed this question to CONFIO, and this is the response from their DBA:  

1. With wait event tuning, the events occurring more frequently will be caught by DBFlash. We do statistical sampling which by definition will miss some things. However, the problems, i.e. the wait events happening more frequently or waiting more time, will be caught by DBFLash. In other words, DBFlash will be able to find your problematic waits which is what you want.

What do you guys think? Is the integrity of the performance data questionable because of the "long" delays between polling? Or is the response from CONFIO valid?  

Thanks!    

Sam Bootsma

George Brown College

sbootsma_at_gbrownc.on.ca <mailto:sbootsma_at_gbrownc.on.ca>

416-415-5000 x4933  

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