Posted by: repettas | August 21, 2014

Quiz night

Originally posted on Oracle Scratchpad:

Here’s a script to create a table, with index, and collect stats on it. Once I’ve collected stats I’ve checked the execution plan to discover that a hint has been ignored (for a well-known reason):

1

Of course we don’t expect the…

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Posted by: repettas | August 19, 2014

Configure the VirtualBox Network

Originally posted on Ed Stevens, DBA:

Configure the VirtualBox Network

In “Create Your Own Test System” I made the case that there is no excuse for someone who considers themselves to be a professional DBA to NOT have their own personal database for testing and learning. I pointed out that by using VMware’s VMplayer, Oracle Linux, and Oracle database under the terms of the developer license agreement, one could create their own private test system legally and at no cost.

I should note that VMware actually has two products that can be used for this purpose. VMplayer is distributed freely, and VMworkstation which costs US$249 as of this writing. (Note: I was rather shocked just now when I checked the current price. When I wrote my original post on the subject, the cost was only US$185.) The difference is that VMplayer is a very bare-bones product, while VMworkstation comes with a very nice management console, full…

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Originally posted on Mathijs Bruggink:

Introduction:

As a dba there should always be some room to improve your backup and recovery scenarios.  This blog is about a  judgment  day scenario – losing a 3TB database in full and your bosses are asking  what will you do and when will the database be back on its feet. In such scenarios I do tend to debate when do you really lose the full database with a need to restore it ..  proper responses might be maybe during an upgrade  to a newer Oracle Release or when you lose the server where the  database is running (however  given the fact that  a lot of sites use SAN  that would even  offer other options than a restore of such a big database not that likely).  In my experience it would be much more common to come across scenarios to restore single datafiles , tablespaces . But OK  for the…

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Originally posted on Kevin Closson's Blog: Platforms, Databases and Storage:

This is part 5 in a series: Part I, Part II, Part III, Part IV, Part V.

Synopsis

This blog post is the last word on the matter.

Enabled?  It’s About Usage!

You don’t get charged for Oracle feature usage unless you use the feature. So why does Oracle inconsistently use the word enabled when we care about usage? If enabled precedes usage then enabled is a sanctified term. Please read on…

It’s All About Getting The Last Word? No, It’s About Taking Care Of Customers.

On August 6, 2014  Oracle shared their last word and official statement on the matter of bug-ridden tracking of the Oracle Database 12c  In-Memory feature usage in a quote to the press at CBR. I’ll paraphrase first and then quote the article. Here is what I hear when I read the words of Oracle’s spokesman:

Yeah, my bad, we…

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Posted by: repettas | August 19, 2014

Dropping redo groups in Another Thread

Originally posted on Mathijs Bruggink:

Introduction:

Quite some time ago I had to turn a Rac environment into a single Instance / Database. However I did notice there where still redo groups of the second instance present which I wanted to drop. This is just a quick blog  to show steps I have followed :

## Checking about the redologs and the thread information:

SQL> select * from v$log;

GROUP#   THREAD# SEQUENCE#     BYTES BLOCKSIZE      MEMBERS ARC STATUS          FIRST_CHANGE# FIRST_TIME      NEXT_CHANGE# NEXT_TIME

———- ———- ———- ———- ———- ———- — —————- ————- ——————- ———— ——————-

1         1      1931 2147483648       512         2 YES INACTIVE         1.3789E+13 14.08.2014 18:46:19   1.3789E+13 18.08.2014 07:08:18

2         1      1933 2147483648       512         2 YES INACTIVE         1.3789E+13 18.08.2014 07:08:20   1.3789E+13 18.08.2014 07:08:22

3         1      1934 2147483648       512         2 NO CURRENT          1.3789E+13 18.08.2014 07:08:22   2.8147E+14

4         2        128 2147483648       512         2 YES INACTIVE        …

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Posted by: repettas | August 12, 2014

Field Notes: BlogHer ’14

Originally posted on WordPress.com News:

Automatticians, the people who build WordPress.com, participate in events and projects around the world every day. Periodically, they report back on the exciting things they do when not in front of a computer. Today, Michelle Weber — one of a group of Automatticians offering real-life happiness engineering at BlogHer ’14 — reports back from the popular women bloggers conference.

BlogHer is an amazing organization created to support and lift up women bloggers. They’re home to blogging communities close to our hearts, like NaBloPoMo, and their conferences are among my favorite blogging events to attend.

Meeting the bloggers who take WordPress and infuse it with their words and images is rewarding, educational, and just fun. This year’s annual conference was no exception — the WordPress booth included a Happiness Bar for on-the-spot troubleshooting, ample hangout space, and, of course, a comfy couch for much-needed conference breaks and blogging tête-à-têtes.

This year…

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Posted by: repettas | August 12, 2014

Read consistency overhead

Originally posted on Oracle Diagnostician:

SQL performance can degrade for many reasons, some of most common are:
– plan changes
– data skewness
– low caching efficiency
– data growth
– contention.

All these factors are relatively well known. A somewhat less common, although not exceptionally rare scenario, is read consistency overhead due to concurrent DML against queried tables. Because of being less common, this scenario is often overlooked, which leads to false diagnoses (and eventually to “fixes” that can do more harm than good).

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Posted by: repettas | August 12, 2014

ASH basics

Originally posted on Oracle Diagnostician:

Introduction

Active session history (ASH), available since 10g, is one of the greatest performance troubleshooting tools available for Oracle databases. And one of most underutilized, too. In this article I will give some basic guidelines regarding ASH usage, and will list some of my favorite ASH queries.

ASH is a view (V$ACTIVE_SESSION_HISTORY). It can give most of the information found in trace files, but unlike tracing, it’s always on!

Using ASH is extremely simple, because you don’t have enable any events or go to database server filesystem to retrieve the results: you just query the view. However, there are a few basic rules that allow to use ASH with maximum efficiency, and minize the risk of misinterpreting its output.

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Posted by: repettas | August 11, 2014

Peeling through layers of cache

Originally posted on Oracle Diagnostician:

Nowadays, data in databases is wrapped in may layers of cache: result cache, buffer cache, OS page cache, storage hardware cache… They greatly improve performance, but they also make it less stable and harder to predict. And when I/O performance takes a turn for worse, one has to go through multiple layers of cache trying to understand what went wrong and why. I had such a case not too long ago.

The incident took place on an Oracle 11.2.0.3 database running on a Solaris 10 server. The first symptom was decreased throughput of one of batch processes in the database by about 30 percent. Since the process was spending more than half of its time doing I/O (as ASH indicated), it was easy to establish that the slowdown was linked to increased time of db file sequential reads by plotting average wait times from DBA_HIST_SYSTEM_EVENT (the SQL code for this…

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Posted by: repettas | August 7, 2014

ODI SendMail

Originally posted on Gurcan Orhan's Oracle Data Integrator Blog:

Here is a brief description how you can handle ODI Sendmail command. This command is quite useful to send mails on errors or success in flow.
First of all ODISendMail can be used in ODI packages by drag and drop under in Toolbox. Here is a short explanation;

REFRESH CUBE : A simple procedure that starts the cube refreshment job.
P_CHECK_CUBES : A scenario that checks whether cube is refreshed or not. Succeeds when cube refresh process finishes successfully.
V_CUBE_MAIL_BODY : Refreshes a variable to be used in mail’s body section. Includes a select statement for descriptive usage.
OdiSendMail 25 : This is the pain point. Sends the prepared mail. Properties are below;

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