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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

Sharing a tablespace between 2 databases

I was reading an interesting discussion today about multiple databases each containing large amounts of read-only data.  If that read-only data is common, then it would make sense to have a single copy of that data and have both databases share it.

Well, as long as you can isolate that data into its own tablespace, then you can do that easily with Oracle by transporting the metadata between two databases and leaving the files in place.

Here’s an example

Source database

SUM is better than DISTINCT

There is a good chance that (based on this blog post title) that you’re expecting a post on SQL, and that’s understandable. But I’ll come clean nice and early – that was just to lure you in Smile 

The post is about SUM and DISTINCT, but not in the technical sense.

Ask Jonathan

Oracle Scene, the magazine of the UK Oracle User Group is piloting a new regular feature called Ask Jonathan,  a chance to get an answer to any question you may have about how the Oracle database engine works.

I’m aiming to answer two or three questions per issue over the course of the year, using a format similar to the one Tom Kyte used in Oracle Magazine:  so if you have a question about the mechanisms, strategies, or mathematics of how Oracle does its thing then attach it as a comment to this posting.

Ideally the questions will have to be quite short (no 20MB trace files, massive schema definitions, or convoluted and exotic setup requirements or it will be too long), and I’ll aim to write something like half a page of in response.  I may summarise the question, or pick out the most interesting feature if it’s a bit too long to publish and answer in its entirety.


Apex Interactive Grid and IOT’s

I love the interactive grid in Application Express.  And here’s why… (Warning: Ranting mode is now on Smile)

You can tell people

Apex patch for 5.1

If you are running Application Express, there is a new patch available.  Lots of fixes which you can read about here

I just downloaded patch 25341386 and followed the installation instructions and it went through with no problems at all in just a few minutes.

End of an era …

Four years ago I wrote about a little volunteer project that my partner did.  A small association that provided outdoor experiences and facilities for kids with physical impairments needed a system to record member and volunteer details, plus a few other bits and pieces.  We built an Apex solution running on XE.  This week, they became part of a larger government initiative, and thus their Apex application was no longer needed and the information migrated to a centralised service.  There was a tinge of sadness about that, but I also was pleased with the outcomes of this “project” namely:

benchmarking your disks


While at Delphix, we did a lot of storage benchmarking. The I/O response times of Delphix depends, as one would logically imagine, heavily on the underlying disks. Sure Delphix can cache a lot ( with 1 TB of ram and 3x compression that’s 3TB and that 3TB can be shared by 10 or a 100 copies being the equivalent to 30TB or 300TB of databases) but really there will always be important I/O coming from the storage subsystem.

Now Delphix mainly runs databases loads, so the best test for storage that is hooked up to Delphix is to benchmark the storage I/O for a database workload. Two questions arise

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 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 - 64bit Production

SQL> select * from regions;

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

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

Pi Day, March 14

Geeks around the world will be celebrating Pi day, a shameless excuse to put the month before the day like the Americans do so we can talk Mathematics on “3.14” day Smile

So what better way to show how cool SQL can be with some expressions to approach Pi with continuous series

All we really need to know by way of background is the CONNECT BY LEVEL trick to generate arbirtary sequences of row, eg

SQL> select level from dual connect by level <= 5;


Now we can get some approximations to Pi using the some of the standard SQL functions SQRT and POWER