UKOUG Northern Technology Summit


Here at the UKOUG, we’ve just announced that we will be holding a 1-day UKOUG Northern Technology Summit in the North of England on the week commencing 16th April 2018.

We have not finalised the location yet, but it will be in either Manchester or Leeds.

This is a 5-stream 1 day event, with around 30 talks! We’d call it a conference – it’s bigger than some European national conferences! – but we don’t want to have any confusion with our sexy flagship conference, UKOUG Tech17.

The Call For Papers is now Open, and we are looking for talks in relation to Database, RAC, Cloud, Apex, Development and Engineered Systems. A full list can be found on the CfP page, linked here.

Tweet about it with the hashtag #UKOUG_ntech

HrOUG – The Croatian Conference

Arriving on Tuesday afternoon, directly from the Slovenia Conference and it’s straight into the 3rd Autumn conference! Conveniently, Slovenia and Croatia are timed together and are held within a little over 1 hours drive (plus a 15 minute boat ride!) apart. Well done on that one guys!IMG_1892

A quiet beer as many speakers and delegates wait at the docks for the boat to arrive, and I seem to be timing these sunsets well!IMG_1795

Wednesday was a day off, so Tuesday night allowed me to let my hair down a little and have a drink until late into the night. Wedneday, and the organizer, Davor, had arranged for all of the Oracle ACEs and Oakies to go on a tour of nearby Pula followed by some Go Karting. Great fun! I knew nothing of Pula so I was rather surprised to discover a huge Amphitheatre there!

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The talks, on Thursday and Friday, were a repeat of the talks in Slovenia about Histograms and Plan Stability.  A great conference in a truely excellent location – having the conference on an island gives it the same magic as the OUGN conference: you can’t just wander off, we are all there together and that really adds to the conference.


Rovinj with Andrew!

As a added bonus, one of my friends happened to be in the nearby town of Rovinj on the Friiday afternoon, which meant a serendipidous meet-up for lunch.

Overall a wonderful pair of conferences which felt as much a holiday as work, although I think I need a holiday to recover from them.

SiOUG – The Slovenian Conference

So October came around and it was time for my second and third conferences of the autumn season.  I had been kindly select to do 2 talks at this Slovenian User Group, but a last-minute problem with another speaker meant I found myself giving 3 talks in 2 days. Excellent fun!IMG_1728


I arrived in lovely Portoroz just as the sun was setting, with what seemed like most of Slovenia leaving the coast on the final hot Sunday of the year, just in time for a huge and wonderful dinner with all of the other speakers.

Day 1 was a whirlwind of talks, food and presenting  much of what I know about Histograms and Chocolate, washed down with a local craft ale – Thank You HumanFish Brewery! Yum!

A party at the end of day 1, with a generous consumption of wine and Craft Ale – all consumed with the lovely friendly and fun Slovenians at the conference – y’all know who you are! – meant that Day 2 held some trepidation…. would I wake up in time!

Day 2 saw me giving 2 more talks, about Optimizer Plan Stability, and also about DataGuard, in front of an interested and good sized audience before hopping into my car and driving down to Croatia to give 2 talks in a somewhat more leisurely 3 days. Tomorrow is a day off! Holiday!

UKOUG RAC SIG, September 27th

There’s a UKOUG RAC SIG on the 27th of September in London.

There a range of great speakers talking about topics from the new RAC Domain Clusters, 12.2 Upgrading, Patching Exadata, and much more.

It’ll be great, it’s true! See you there…

Online Index Rebuild Problem in 12C

When building an index in Oracle Enterprise edition using the keyword “ONLINE”, if the index build fails for whatever reason a messy set of extents can get left behind.

In Oracle 12.1 there’s a new job to help with this: “SYS”.”CLEANUP_ONLINE_IND_BUILD” which ticks away, undocumented, in the background cleaning up “rogue” extents once an hour, every hour (start time based upon job creation time)However, if I run a CREATE INDEX … ONLINE command on a table and the index creation happens to coincide with the invocation of the cleanup job I get the following error in my alert log

ADR Home = /u01/app/oracle/diag/rdbms/orcl/orcl1:
2017-05-12 05:28:37.191123 -04:00
Errors in file /u01/app/oracle/diag/rdbms/orcl/orcl1/trace/orcl1_j000_12235.trc:
ORA-12012: error on auto execute of job "SYS"."CLEANUP_ONLINE_IND_BUILD"
ORA-00054: resource busy and acquire with NOWAIT specified or timeout expired
ORA-06512: at "SYS.DBMS_PDB", line 76
ORA-06512: at line 4

Oh no! The job has failed to clean up the extents that I was currently using. Phew!

The CREATE INDEX … ONLINE command completed with success a few minutes later.

A few minutes after that, an update statement failed with:

ORA-08102 index key not found for obj# 107102 file 16 block 1171234

Yes, I have a corrupt index! index_fadeMy assumption is that the cleanup job had removed all of the extents which had been allocated before the cleanup job started. The index create statement did not notice as the current extent removal attempt blocked (hence the job error) and future to-be created extents were not affected. However, most of the index had been “cleaned up”. #sadface

Solution: re-create the index and make sure the index creation is complete before your hourly job kicks in. Better still, disable the undocumented hourly job… make sure get the full backing of an Oracle Support SR first!

Next Step: Raise SR with Oracle about this!


GoldenGate unsupported types

When using GoldenGate there are few rules which need to be followed, and a very small number of unsupported datatypes. This is the excerpt from the GoldenGate 12.2 manual:



1.6.10 Non-Supported Oracle Data Types
Oracle GoldenGate does not support the following data types.

 ANYDATA fetch-based column support for data types with VARRAYS that do not include named collections and VARRAYS embedded within those data types
 UDT with containing an unsupported Oracle Data Type
 Oracle GoldenGate does not support replication of identity column data or Valid Time Temporal column data.

One of those may be more common that you think – the last bullet point is the Oracle 12C datatype IDENTITY. The following code snippet is not supported for replication by GoldenGate

create table with_identity
( COL_ID    number(38) generated always as identity minvalue 1 not null enable,
  text_info varchar2(10),
  constraint with_identity_pk  primary key (COL_ID) );

insert into with_identity (text_info) values ('Row 1');


desc with_identity
 Name                          Null?    Type
 ----------------------------- -------- --------------------
 COL_ID                        NOT NULL NUMBER(38)
 TEXT_INFO                              VARCHAR2(10)

You can see that it is an identity column in user_tab_columns:

select TABLE_NAME,COLUMN_NAME,IDENTITY_COLUMN from user_tab_columns where table_name = 'WITH_IDENTITY';

TABLE_NAME                     COLUMN_NAME                    IDE
------------------------------ ------------------------------ ---
WITH_IDENTITY                  COL_ID                         YES
WITH_IDENTITY                  TEXT_INFO                      NO

So, how does GoldenGate alert you to the fact that it will not be replicating this table with an unsupported type? It doesn’t.

look in ggserr.log – nothing
look in the extract report file for wildcard matching the table – nothing

With a table containing an unsupported data type, the lack of replication is silent because GoldenGate is completely ignoring the object. Completely Silently.

So, how could I have picked this up before it became a problem?

Obviously I need to run the script in MOS article 1296168.1, which analyzes your schema for GoldenGate compatiblity. Unfortunately, Oracle have not updated this to account for IDENTITY columns, so there is no indication that it does not work!

The script to run is the GoldenGate Integrated Extract Healthcheck script, found in MOS article 1448324.1

Finally some vague and unclear indication that we may have a problem. Part way through the report we get this:

Lists tables that can not be supported by OGG (NONE)
Lists table that are supported via OGG FETCH (ID KEY)

Owner           OBJECT_NAME             SUPPOR  Container ID
HR              WITH_IDENTITY         ID KEY     3

Always take care with GoldenGate – it’s not just a plug-in solution. You need to think about the implementaiton and work with the application to get the best outcomes.

Getting Started with GoldenGate

gettingstartedwithgoldengateNot a blog post per-se, but a link to my article in the UKOUG quarterly magazine OracleScene. It is a great publication with some simply fantastic articles. Its completely free, and is available online as well as in print at Oracle offices in the UK and at UKOUG events. My article will take you through a simple step-by-step Oracle centric one way replication on VM Virtual Box. From nothing to fully working replication. Sexy! Hope you enjoy it.

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