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October 2014

EM12c Release 4, Health Overview

As part of the projects I work on at Oracle, it’s often ensuring that those customers that wish to deploy Enterprise Manager, (EM12c) to large environments, have the correct settings and are tuned to offer the best performance from the Oracle Management repository database, weblogic and up to the console URL’s accessed by users.  This means that these large environments often receive recommendations from our experts  th

The First PASS Summit Bloggers’ Meetup

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We are stoked to announce the first ever PASS Summit Bloggers’ Meetup! /> /> What: PASS Summit Bloggers’ Meetup 2014 /> When: Thursday, November 6th, 5pm – 7pm /> Where: Sports Restaurant & Bar, 140 4th Ave North, Suite 130, Seattle, WA 98109 /> How: Please comment with “COUNT ME IN” if coming — we need to know attendance numbers.

We’re excited to meet old friends, and make new ones in Seattle this year. Pythian will sponsor munchies and drinks. There will be a networking contest with some cool prizes, plus everyone will get their very own PASS Summit Bloggers Meetup shirt! Meetups are a great way to make new friends in the community, so come on out — all bloggers are welcome!


No, not the 10th posting about first_rows() this week – whatever it may seem like – just an example that happens to use the “calculate costs for fetching the first 10 rows” optimizer strategy and does it badly. I think it’s a bug, but it’s certainly a defect that is a poster case for the inherent risk of using anything other than all_rows optimisation.  Here’s some code to build a couple of sample tables:

Interesting observations executing SLOB2 with ext4 and xfs on SSD

My lab server has 2 SSDs, one is connected using SATA 2 and another is connected using SATA 3. I’d expect the SATA 3 connected device to be equally well equipped or even better to do work than the “old” interface. I ran SLOB on these devices to find out if there was a difference. To my great surprise the SATA2 – connected SSD performed a lot better than the SATA 3 device, as shown in the AWR report! Initially I was not entirely sure why, since the FIO results on both devices are roughly equal. You will see why though when reading this post. In summary: use XFS for any concurrent writes. Or maybe ASM.

Let’s investigate

Let’s do a little I/O investigation because a) it’s cool and b) you can.

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:

Index Advanced Compression vs. Bitmap Indexes (Candidate)

A good question from Robert Thorneycroft I thought warranted its own post. He asked: “I have a question regarding bitmapped indexes verses index compression. In your previous blog titled ‘So What Is A Good Cardinality Estimate For A Bitmap Index Column ? (Song 2)’ you came to the conclusion that ‘500,000 distinct values in a 1 […]

HPC versus HDFS: Scientific versus Social

There have been rumblings from the HPC community indicating a general suspicion of and disdain for Big Data technology which would lead one to believe that whatever Google, Facebook and Twitter do with their supercomputers is not important enough to warrant seriousness—that social supercomputing is simply not worthy.  A little of this emotion seems to […]

Quiz night

Here’s a little puzzle that came up on OTN recently.  (No prizes for following the URL to find the answer) (Actually, no prizes anyway). There’s more in the original code sample than was really needed, so although I’ve done a basic cut and paste from the original I’ve also eliminated a few lines of the text: Introduction to Zone Maps Part II (Changes)

In Part I, I discussed how Zone Maps are new index like structures, similar to Exadata Storage Indexes, that enables the “pruning” of disk blocks during accesses of the table by storing the min and max values of selected columns for each “zone” of a table. A Zone being a range of contiguous (8M) blocks. I […]

Metric Thresholds and the Power to Adapt

Metric thresholds have come a long way since I started working with OEM 10g.  I remember how frustrating it could be if an ETL load impacted the metric values that had to be set for a given IO or CPU load for a database when during business hours, a much lower value would be preferable.  Having to explain to the business why a notification wasn’t sent during the day due to the threshold set for resourc