With Modern Storage the Oracle Buffer Cache is Not So Important.

With Oracle’s move towards engineered systems we all know that “more” is being done down at the storage layer and modern storage arrays have hundreds of spindles and massive caches. Does it really matter if data is kept in the Database Buffer Cache anymore?

Yes. Yes it does.

Time for a cool beer

Time for a cool beer

With much larger data sets and the still-real issue of less disk spindles per GB of data, the Oracle database buffer cache (more...)

AWS EC2 API tools: Create snapshot & Check Data in snapshot

After installed AWS EC2 API tools,  It's time for example create/delete snapshot. 
- Creating snapshot.
ubuntu@ip-x-x-x-x~$ ec2-describe-volumes
VOLUME  vol-41885f55    8       snap-d00ac9e4   ap-southeast-1a in-use  2015-05-26T09:07:04+0000        gp2     24
ATTACHMENT      vol-41885f55    i-d6cdb71a      /dev/sda1       attached        2015-05-26T09:07:04+0000        true
ubuntu@ip-x-x-x-x:~$ ec2-create-snapshot  -d vol-41885f55-$(date +%Y%m%d%H%M) vol-41885f55
SNAPSHOT        snap-b20a8c87   vol-41885f55    pending 2015-05-27T05:46:58+0000 (more...)

AWS EC2 API tools: Installation

AWS EC2 API tools help too much for Amazon EC2 to register and launch instances, manipulate security groups, and more. Someone asked me to backup EC2 instance. I thought to use it for backup script. Anyway, No need to explain more how to install Amazon EC2 API tools on Ubuntu? Just say thank for  EC2StartersGuide. I fellow this link and installed it easily. Additional, I used this Link for more idea about java.
- Adding (more...)

Oracle Database 12c – Active Duplication with RMAN (in Spanish Language)

Oracle Technology Network - OTN Latina published our "Pull-Based Active Duplication with RMAN" article series this month in Spanish Language. This article series covers new option of duplication with RMAN on Oracle Database 12c Release 1 (12.1.0.1) in 11 parts.



First part of article series described "how to duplicate database" and other parts showed different cases of CDB and PDBs duplication.You can read articles here


 Oracle Database 12c: Active Duplication con RMAN (more...)

Writing Tips : Can I get paid to write?

writingI’ll prefix this post with a warning. I’ve never done any paid blogging myself, so this is based on emails I’ve received from people requesting me to write for them and from comments I’ve heard from others. With that in mind…

Apart from having adverts on your blog or selling books, there are other ways to earn money from writing. You will have to decide if they suit you.

Paid Articles. Some websites, blogs and magazines pay for (more...)

Stop That!


"It seems to me that almost everything is a waste of time."
- Norton Juster, The Phantom Tollbooth 

Jonathan Lewis has coined a term and its definition that, I believe, we’ll be using quite a bit:



Stoptimisation - the art of optimisation by not doing the things you don't need to do.

It’s a term we’ve needed for some time now, given the pendulum swing back to the days of yore (meaning pre-9i) with (more...)

Making Existing SQLPLUS Scripts 12c and Container DB (PDB) Compatible

Oracle 12c introduces new catalog features including CDB_ dictionary views (which include a CON_ID column) superseding the DBA_ views that most DBA sqlplus scripts are based upon.

However, existing DBA sqlplus scripts can easily be modified using just a few simple sqlplus techniques to be compatible with 11g, as well as all types of 12c databases including legacy and container databases.

The following simple SQL and sqlplus techniques can be used to make a “universal (more...)

SQL Performance, Part IV. Heap tables.

Demo script


CHEP 2015 papers on replication and scale-out databases

CHEP 2015, the 21st international conference on computing in high energy physics, has taken place in April 2015 in Okinawa, Japan. Here below you can find the links to the pdf of the talks, posters and related preprints of two of the contributions by members the CERN database group. These are on the topics of our tests with scale-out databases (in particular on the Hadoop platform) and on the evolution of the replication technologies (more...)

Lab Report: Oracle Database on EMC XtremIO. A Compression Technology Case Study.

If you are interested in array-level data reduction services and how such technology mixes with Oracle Database application-level compression (such as Advanced Compression Option), I offer the link below to an EMC Lab Report on this very topic.

To read the entire Lab Report please click the following link:   Click Here.

The following is an excerpt from the Lab Report:

Executive Summary
EMC XtremIO storage array offers powerful data reduction features. In addition to (more...)

Writing Tips : How can I make money?

writingYou’ve started a blog. This time next year you’re going to be a millionaire!

If you are interested in making money from a website you can. There are a number of advertising options, with the most popular for the small publishers being Google Adsense. Having said that, you’re going to get a rude awakening when you start earning 20 cents a day.

Advertisers care about reach, so advertising is a numbers game. If you want (more...)

Oracle #DB12c New – MAX_STRING_SIZE

In pre-12c database releases, VARCHAR2, NVARCHAR2 data types were limited to 4000 bytes and RAW data type was limited to 2000 bytes. If there is a need to store more data in VARCHAR2 column, you can in 12c after setting the parameter MAX_STRING_SIZE to EXTENDED. With setting MAX_STRING_SIZE to EXTENDED, you can store up to […]

Smart Scan enhancements in Oracle Exadata 12c-inline LOBs

As part of the 12c release of the database and cellos Oracle introduced the ability to perform Smart Scans on inline LOBs. The enhancement is certainly for Secure Files only. And as always, if you would like to read up about Secure Files you can head over to Tim Hall’s website for the details.

To demonstrate the new behaviour I have used an 11.2.0.3 BP 22 database on Exadata 11.2.3. (more...)

Temp Table Transformation Cardinality Estimates – 1

Having published recently two notes about the Temp Table Transformation highlighting the heuristics based decision and other weaknesses, for example regarding the projection of columns, it's time to publish some more notes about it.The transformation can also have significant impact on cardinality estimates, both join and single table cardinality.Looking at the difference in the join cardinality estimates of following simple example:

create table t1
as
select
rownum as id
, mod(rownum, 10) (more...)

Writing Tips : A URL is for life, not just for Christmas!

writingI’m currently doing yet another pass through my whole website correcting broken external links. This is nothing to do with my bad management. This is to do with people changing their URLs and not putting the correct redirects in place. I’ve just done a scan of my website and there are over 800 broken links to Oracle documentation!

There seem to be several ways people deal with URL changes on their website.

Datapump TTS quick tip

I was trying to transport a large number of tablespace datafiles from one database to another, and impdp kept crashing with “PL/SQL: numeric or value error: character string buffer too small.”

It turns out there is a limit on what you can put on a single line in a parameter file.  Hence if you have something like:

transport_datafiles=/long/path/file1,/long/path/file2,/long/path/file3,....

then you might run into trouble. It’s easily fixed however – just put the entries (more...)

Tracing Single SQL in Oracle

Many times, while doing SQL tuning, we want to trace (event 10046) single SQL in database. Instead of going for module level tracing or session level using DBMS_MONITOR, we can simply use below alter system command to trace specific SQL

Example: I have a table T1 and index T_I_TABLE_NAME on that table.
I am running following SQL and I want to trace on this SQL

select * from T1 where table_name = 'SINGLE_PRODUCT_GROUPS';

I (more...)

direct path read behavior in Oracle 11.2

Prior to 11g, whenever optimizer goes for full table scan, Oracle used to show “db file scattered read” as wait event. But starting from 11g, a full table scan can show (depending on certain conditions) “direct path read” wait event.

db file scattered read – happens when blocks for a table is read from datafile into buffer cache in SGA

direct path read – happens when blocks for a table is read from datafile into (more...)

Recover Oracle Undo Tablespace without Backup

Woke up with an issue regarding a Oracle 10.2.0 database on Linux complaining about an Undo file on startup.


sqlplus '/ as sysdba'

SQL*Plus: Release 10.2.0.3.0 - Production on Fri May 22 20:11:07 2015

Copyright (c) 1982, 2006, Oracle.  All Rights Reserved.

Connected to an idle instance.

SQL> startup pfile='init.ora'
ORACLE instance started.

Total System Global Area 2801795072 bytes
Fixed Size                  2075504 bytes
Variable Size            1275069584 bytes
(more...)

From Product X to SQL Developer

I recently worked at a company that used "Product X" for all of it SQL and PL/SQL activities.  There’s no real need to reveal what "Product X" is, because this isn’t a post about whether as a product it was good, bad or somewhere in between.  "Product X" met the needs of the Oracle developers in the company, and that’s all that matters.  There was just one issue – for Product X, (more...)