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PostgreSQL Invalid Page and Checksum Verification Failed

At the Seattle PostgreSQL User Group meetup this past Tuesday, we got onto the topic of invalid pages in PostgreSQL. It was a fun discussion and it made me realize that it’d be worth writing down a bunch of the stuff we talked about – it might be interesting to a few more people too!

Invalid Page In Block

You see an error message that looks like this:

PostgreSQL Invalid Page and Checksum Verification Failed

At the Seattle PostgreSQL User Group meetup this past Tuesday, we got onto the topic of invalid pages in PostgreSQL. It was a fun discussion and it made me realize that it’d be worth writing down a bunch of the stuff we talked about – it might be interesting to a few more people too!

Invalid Page In Block

You see an error message that looks like this:

PostgreSQL Invalid Page and Checksum Verification Failed

At the Seattle PostgreSQL User Group meetup this past Tuesday, we got onto the topic of invalid pages in PostgreSQL. It was a fun discussion and it made me realize that it’d be worth writing down a bunch of the stuff we talked about – it might be interesting to a few more people too!

Invalid Page In Block

You see an error message that looks like this:

Introduction to Intel Pin

This blogpost is an introduction to Intel’s Pin dynamic instrumentation framework. Pin and the pintools were brought to my attention by Mahmoud Hatem in his blogpost Tracing Memory access of an oracle process: Intel PinTools. The Pin framework provides an API that abstracts instruction-set specifics (on the CPU layer). Because this is a dynamic binary instrumentation tool, it requires no recompiling of source code. This means we can use it with programs like the Oracle database executable.
The Pin framework download comes with a set of pre-created tools called ‘Pintools’. Some of these tools are really useful for Oracle investigation and research.

Why ALL Tools in at Your Disposal ARE IMPORTANT

After my AWR Warehouse session at DOAG in Nuremberg, Germany last week, an attendee asked me if he really needed to use trace files anymore with the value provided by AWR, (Automatic Workload Repository) and ASH, (Active Session History.)  I responded that trace files were incredibly val

MySQL : What management tools do you use?

A quick question out to the world. What management tools do you use for MySQL?

We currently have:

Enabling and Reading event 10046 / SQL Trace

As I’m done with the book and back from a quick vacation (to Prague, which is an awesome place – well, at least during the summer) I promised (in Twitter) that now I’d start regularly writing blog articles again. In a separate tweet I asked what to write about. Among other requests (which I’ll write about later), one of the requests was to write something about enabling and reading SQL trace files… 

I am probably not going to write (much) about SQL trace for a single reason – Cary Millsap has already written a paper so good about this topic, that there’s no point for me to try to repeat it (and my paper wouldn’t probably be as clear as Cary’s).

So, if you want to get the most out of SQL Trace, read Cary’s Mastering Performance with Extended SQL Trace paper:

 

The above link directs you to Method-R’s article index, as there’s a lot of other useful stuff to read there.

Wow, now I’m done with my first request – to write something about SQL Trace :-)

 

Cache buffers chains latch contention troubleshooting using latchprofx.sql example

Laurent Demaret has written a good article about how he systematically troubleshooted cache buffers chains latch contention, starting from wait interface and drilling down into details with my latchprofx tool:

A common cause for cache buffers chains latch contention is that some blocks are visited and re-visited way too much by a query execution. This usually happens due to nested loops joins or FILTER loops retrieving many rows from their outer (driving) row sources and then visiting the inner row-source again for each row from driving row source. Once you manage to fix your execution plan (perhaps by getting a hash join instead of the loop), then the blocks will not be re-visited so much and the latches will be hammered much less too.

The moral of the story is that if you have latch contention in a modern Oracle database, you don’t need to start tweaking undocumented latching parameters, but reduce the latch usage instead. And Laurent has done a good job with systematically identifying the SQL that needs to be fixed.

Good stuff!

If you don’t know what LatchProfX is, read this:

 

New scripts, tools and broken links

I have some broken links in my old blog entries right now, so if you’re looking for something, then download the whole zip file from here:

I have uploaded a .zip file (for Windows) and a .tar.gz file (for Unix/Mac). The scripts are all the same with differences in the CR/LF bytes in the files and the init.sql and i.sql which have some OS specific commands in them.

I also uploaded the latest PerfSheet there where I fixed an annoying bug which complained about some missing reference files when opening the file.

I plan to fix the broken links some time between now and my retirement.

 

MOATS: The Mother of All Tuning Scripts!

People talk about the Oracle SQL Developer 3 being out, which is cool, but I have something even cooler for you today ;-)

I finally figured out how to convert my screen-recordings to uploadable videos, so that the text wouldn’t get unreadable and blurry.

So, here’s the first video, about a tool called MOATS, which we have built together with fellow OakTable Network member and a PL/SQL wizard Adrian Billington (of oracle-developer.net).

Here’s the video, it’s under 3 minutes long. Play the video in full screen for best results (and if it’s too slow loading, change it to lower resolution from HD mode):

Check it out and if you like MOATS, you can download it from Adrian’s website site (current version 1.05) and make sure you read the README.txt file in the zip!

Also thanks to Randolf Geist for finding and fixing some bugs in our alpha code… Note that MOATS is still kind of beta right now…

P.S. I will post my ORA-4031 and shared pool hacking video real soon now, too! :-)

P.P.S. Have you already figured out how it works?! ;-)

Update: Now you can suggest new features and improvement requests here: