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12c

Parallelism

Headline – if you don’t want to read the note – the /*+ parallel(N) */ hint doesn’t mean a query will use parallel execution, even if there are enough parallel execution server processes to make it possible. The parallel(N) hint tells the optimizer to consider the cost of using parallel execution for each path that it examines, but ultimately the optimizer will still take the lowest cost path (bar the odd few special cases) and that path could turn out to be a serial path.

The likelihood of parallelism appearing for a given query changes across versions of Oracle so you can be fooled into thinking you’re seeing bugs as you test new versions but it’s (almost certainly) the same old rule being applied in different circumstances. Here’s an example – which I’ll start off on 11.2.0.4:

255 Again!

There are so many things that can go wrong when you start using tables with more than 255 columns – here’s one I discovered partly because I was thinking about a client requirement, partly because I had a vague memory of a change in behaviour in 12c and Stefan Koehler pointed me to a blog note by Sayan Malakshinov when I asked the Oak Table if anyone remembered seeing the relevant note. Enough of the roundabout route, I’m going to start with a bit of code to create a table, stick a row in it, then update that row:

Transportable Tablespace–part 2

I did a little demo of sharing a tablespace between two databases a few days back – you can see the details here or by just scrolling down Smile if you’re on the home page.

To avoid clouding the demonstration I omitted something in the details, but I’ll share that now, because it could be critical depending on how you currently use transportable tablespaces.

Let me do the most basic of examples now, transporting a tablespace from one database to another:

First, we make our tablespace read only, and Datapump export out the metadata

IOUG Collaborate 2017

I have a few presentations scheduled in IOUG Collaborate 2017, Las Vegas.

1. Session: 621: RAC Clusterware internals
**Date/time: Mon, Apr 03, 2017 (01:30 PM – 02:30 PM) : Jasmine A

2. Session: RAC cache fusion internals. ( OakTable track )
**Date/time: Wed, Apr 05, 2017 (09:45 AM – 10:45 AM) Room: South Seas C

3. Session: 479: An in-depth review of ASM and internals
**Date/time: Wed, Apr 05, 2017 (02:45 PM – 03:45 PM) : Palm B

Presentation files ( Updated after the presentations).

Thank you for coming to my presentation(s).

12c Release 2, set feedback enhancement in SQL PLus

There’s a nice little touch to the “set feedback” command in SQL PLus in 12.2. There is a new “only” clause in the SET FEEDBACK command, so you can run queries but the resulting rows are not shown in the display. They are still queried, fetched and “returned”, but just rendered to the screen. Here’s an example


$ sqlplus hr/hr

SQL*Plus: Release 12.2.0.1.0 Production on Tue Mar 14 22:59:15 2017

Copyright (c) 1982, 2016, Oracle.  All rights reserved.

Last Successful login time: Sat Mar 11 2017 01:59:20 -04:00

Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production

SQL> select * from regions;

 REGION_ID REGION_NAME
---------- -------------------------
         1 Europe
         2 Americas
         3 Asia
         4 Middle East and Africa

So that’s normal behaviour. Let’s now use the new ONLY option.

12c Release 2 – Transparent Data Encryption online !

It doesn’t take a rocket scientist to know that even if you have incredibly stringent controls on user authentication, user authorisation etc, that wont save you if your data on disk is not encrypted.  All you need is an errant tape, a missing disk, a misplaced flash stick…and kersplat, someone has a copy of your datafiles from your Oracle database.

Data at rest should be encrypted, but that often meant taking applications offline to do so.

I’ve put my Speed Racer hat on Smile and here’s a video on a new 12c Release 2 feature covered in 60 seconds !

TimTams, Twelve Two, and tete-a-tete !

What do you do when

  • you’re an Australian,
  • you’re at Oracle Headquarters, 13,000 kms from home
  • you bump into someone whilst grabbing a coffee

Well…naturally, you lure them over with a packet of our famous Australian chocolate biscuits, grab a camera and have a chat !

Maria Colgan and I chew the fat over why you should upgrade to Oracle Database 12c (including Release 2)

Oracle Database 12c Release 2 is here !

image

Since OpenWorld 2016 when we first saw some of the cool features in Oracle Database 12c Release 2, many IT professionals out there have been exploring the release via our various cloud offerings, but if your organization has not yet embraced the cloud, then March 2017 is a great month for you !  Because you can now download the latest and greatest release of our database from the usual downloads page, and run it on your own servers in your own data centre.

Truncate 12c

Here’s one of those little improvements in 12c (including 12.1) that will probably end up being described as “little known features” in about 3 years time. Arguably it’s one of those little things that no-one should care about because it’s not the sort of thing you should do on a production system, but that doesn’t mean it won’t be seen in the wild.

Rather than simply state the feature I’m going to demonstrate it, starting with a little code to build a couple of tables with referential integrity:

Band Join 12c

One of the optimizer enhancements that appeared in 12.2 for SQL is the “band join”. that makes certain types of merge join much more  efficient.  Consider the following query (I’ll supply the SQL to create the demonstration at the end of the posting) which joins two tables of 10,000 rows each using a “between” predicate on a column which (just to make it easy to understand the size of the result set)  happens to be unique with sequential values though there’s no index or constraint in place: