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December 2016

12.2 Index Advanced Compression “High” – Part I (High Hopes)

Oracle first introduced Advanced Compression for Indexes in 12.1 as I’ve discussed here a number of times. With Oracle Database 12c Release 2, you can now use Index Advanced Compression “High” to further (and potentially dramatically) improve the index compression ratio.  Instead of simply de-duplicating the index entries within an index leaf block, High Index […]

UKOUG Tech16 Day 0 – Car and Curry Chaos!

This year I decided to come to Birmingham a little early for UKOUG Tech16, coming up on the Saturday. I drove up to Lichfield where I grew up (15 miles North of Brum – which explains the touch of Brummie in my accent) in the morning to see my mum. Once we had discussed her various ailments and prejudices for a few hours and I’d unblocked her vacuum cleaner I set off into Birmingham to get to Jury’s hotel for 18:00. I was sure the shoppers would be pouring out of the city centre by then and it would be quietening down.

GTT and Smart Scan – the importance of the append hint

While writing the previous two posts about GTTs and Smart Scan, I stumbled across an interesting observation. When I started putting my thoughts to (virtual) paper, I thought it was going to be a short post. Well, it wasn’t to be, again. Anyway, you might find this interesting.

Initial Situation

If you read the previous posts this code example I used to populate the GTT might look familiar:

insert /*+ append */ into gtt select * from t4 where rownum < 400000;
 
commit;

In situations like this where I’m moving data I developed a habit of using the append hint. I guess I’ve been working on HCC tables a bit too much and therefore didn’t even make a conscious decision to use that hint. It was the right thing to do, as you will see next.

The full test harness is shown here again for reference:

Amazon announces Performance Insights

Excited to see the announcement of Amazon RDS Performance Insight feature for database performance monitoring and tuning.

Having met the team for this project I can say from my personal view point that the importance and future success of this feature is clear as day to me. The team is awesomely sharp, the architecture is super impressive, and this is by far the most exciting performance monitoring and feedback system I’ve been involved with,  surpassing the work I’ve been involved in on Oracle’s performance monitoring and tuning system and Embarcadero’s DB Optimizer and Quest Foglight and Spotlight. Not only does the feature provide it’s own dashboard but will also provide an API to power your dashboards that already exist in the industry. I expect to see partners leveraging the API to provide new insights in their already existing database performance monitors.

Histogram Upgrade

I’ve written notes in the past about the improvements 12c introduces for histograms – particularly the frequency and top-N histograms which can be generated “free of charge” while the basic “approximate NDV” scans are taking place to gather stats. Gathering histograms in 12c is much safer than it used to be in earlier versions of Oracle even in the case of the new hybrid histograms (which are still sampled on a very small sample and therefore still a stability risk).

Friday Philosophy – Hello….?Dave?

In 2 days time the UKOUG Tech16 conference starts. I love this conference, I’ve been to all but 1 one of them in the last 15 years – but I am not going to go on about why I like it so much again.

How to reduce Buffer Busy Waits with Hash Partitioned Indexes in #Oracle

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Buffer Busy Waits can be a serious problem for large OLTP systems on both tables and indexes. If e.g. many inserts from multiple sessions occur simultaneously, they may have to compete about the same index leaf blocks like the picture below shows:

SQL*PLus on Mac

I would think installing SQL*Plus on the Mac would be point, click download, point click, install bam it works.

Nah

It did install mostly straight forward on my old Mac. Got a new Mac and no dice.

Tried installing myself guessing at the downloads. First of all why isn’t there just one download?

Downloaded instantclient and instantclient with SQL*Plus which turns out to be correct, but no dice. Still got errors.

Got errors. Gave up.

Came back again to look at it yesterday and followed this:

https://tomeuwork.wordpress.com/2014/05/12/how-to-install-oracle-sqlplus-and-oracle-client-in-mac-os/

worked like a charm.

Then I ran a shell script that used SQL*Plus oramon.sh and get the error

Why oh Why Do We Still Not Have a Fast Bulk “SQL*Unloader” Facility?

Way back in 2004 I was working at the UK side of the Human Genome project. We were creating a massive store of DNA sequences in an Oracle database (this was one of two world-wide available stores of this information, for free & open use by anyone {* see note!}). The database was, for back then, enormous at 5-6TB. And we knew it would approx double every 12 months (and it did, it was 28TB when I had to migrate it to Oracle 10 in 2006, over 40TB 6 months later and grew to half a petabyte before it was moved to another organisation). And were contemplating storing similar massive volumes in Oracle – Protein, RNA and other sequence stores, huge numbers of cytological images (sorry, microscope slides).

How Partial Indexing helps you save space in #Oracle 12c

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Over time certain partitions may become less popular. In 12c, you don’t have to index these partitions anymore! This can save huge amounts of space and is one of the best 12c New Features in my opinion. Really a big deal if you are working with range partitioned tables where the phenomenon of old ranges becoming unpopular is very common. Let’s have a look, first at the problem: