Sunday, May 15, 2011

Feedback on Tanel Poder's AOTS #2 Class

In my earlier post I me wrote about Tanel Poder's Virtual Class #2. Tanel is a world famous expert in Oracle internals. I was fortunate to be able to attend the class on all days except Friday. It was solid 4 hours of learning every day. Let me summarize some of the key points I appreciated as an attendee. I hope it will be useful for you making a decision to attend one later.

(1) The beginning of the class explained the concepts like latching and locking pretty well
(2) Next in the line was understanding "why" they occur; not "how much"
(3) Reinforced the fact that latches smell like, look like, behave like locks; and are kind of locks
(4) Differentiated between soft and hard parses and explained the role of cursor_sharing parameter
(5) Differentiated between library cache pins, locks and latches

But if there is only one benefit I can say is priceless, that would be the holistic tuning, using the key concepts to understand the behavior all the way from the user response time to tracing the unix process to understand where the bottlenecks are. Tanel explained all that with a live example to cement that knowledge. All in all, an excellent class by an excellent instructor.

Friday, May 06, 2011

Tanel Poder's Virtual Class #2

On a fine day in some month in some year, a little scene is playing out in Acme Bank's IT department.

Developer (with the best I-told-you-these-DBAs-are morons face) harrumphs, "The database is slow again!!! Does anybody even care?"

Junior DBA enthusiastically responds with a slightly belligerent tone, "Of course we do. I opened a ticket. The ticket# is ...."

Mid-level DBA announces with an officious tone, "The session is waiting for latches" as if explains everything.

Mid-level DBA aspiring to be the top dog chimes in "the session has waited 123.904567 seconds in cache buffer chain latch, 24.096534 seconds in share pool latch, 456.742340 seconds in db file scattered read ...." and rants the list of wait events measured precisely by taking a trace and/or looking at an esoteric mix of v$ and x$ views to drive even Graham Wood mad.

Everyone looks at the Senior DBA, who pronounces with the gravest voice, "my intuition says that this is caused by the application change that went in yesterday"

The developers gasped but before their string of protests flowed in, the user asks innocently, "OK. How do we solve it?"


Exaggeration and over-dramatization aside, I think you will appreciate the simple truth in this scenario, which is not really that far from reality in many cases. At the end of the day you have to"solve" the problem. Measuring the wait events to the precision of micro seconds helps; but does not identify the root cause. You must know what causes the latch. No; you must understand what causes the cache buffer chain latch and then go on a hunt to stamp out the root cause. The tenets of solving a problem are understanding why it happens in the first place, identifying all possible causes, eliminating the irrelevant causes by evidence and finally zeroing on a solution based on findings. Intuition helps; but is not a replacement, not by a long shot, of the understanding the inner workings.

So, Acme hires an "expert", who did all that; but in the end, solved the problem. the junior DBA closed the ticket. Everyone was happy.

Do you want to be that expert? Do you want to poke your head under the hood of the Oracle engine? If so, look no further. Tanel Poder has been hacking the Oracle database since the, oh, I don't know, a long time. He put together all his knowledge into a set of instructional modules and he is offering all that as a virtual class. It's runs May 9th to 12th, 11 AM to 3 PM (US Eastern Time) every day. Interested? Register here

Oh, did I mention that this is a web-based class? That means you don't have to take even a step more for this - you can be on your bed in pajamas or in your cube at work. You get tons of material for learning, hacking and playing with innards of Oracle, along with Tanel's world famous TPT scripts - an alchemist's box for Oracle-geeks.

I am excited to attend; and I highly recommend anyone seriously wishing to be that expert.