Search

Top 60 Oracle Blogs

Recent comments

Oracle

The Security State of the Nation

Even though my social media profile is pretty available for Twitter and Linked in, I’m significantly conservative with other personal and financial data online.  The reversal of the Internet Privacy Rule, (I’ve linked to a Fox news link, as there was so much negative news on this one…) had everyone pretty frustrated, but then we need to look at security of personal information, especially financial data and as we can see by security breaches so far in 2017, we all have reason to be concerned.

Bequeath connect to PDB: set container in logon trigger?

There are little changes when you go to multitenant architecture and one of them is that you must connect with a service name. You cannot connect directly to a PDB with a beaqueath (aka local) connection. This post is about a workaround you may have in mind: create a common user and set a logon trigger to ‘set container’. I do not recommend it and you should really connect with a service. Here is an example.

Imagine that I have a user connecting with bequeath connection to a non-CDB, using user/password without a connection string, the database being determined by the ORACLE_SID. And I want to migrate to CDB without changing anything on the client connection configuration side. The best idea would be to use a service, explicitly or implicitly with TWO_TASK or LOCAL. But let’s imagine that you don’t want to change anything on the client side.

Get trace file from server to client

The old way to get a user dump trace file, for sql_trace (10046), Optimizer compilation trace (10053), lock trace (10704), Optimizer execution trace (10507),… is to go to the server trace directory. But if you don’t have access to the server (as in the ☁) the modern (12cR2) way is to select from V$DIAG_TRACE_FILE_CONTENTS. Before everybody is on 12.2 I’m sharing here a sqlplus script that I use for a long time to get the trace file to the client.

Postgres vs. Oracle access paths VIII – Index Scan and Filter

In the previous post we have seen a nice optimization to lower the consequences of bad correlation between the index and the table physical order: a bitmap, which may include false positives and then requires a ‘recheck’ of the condition, but with the goal to read each page only once. Now we are back to the well-clustered table where we have seen two possible access paths: IndexOnlyScan when all columns we need are in the index, and IndexScan when we select additional columns. Here is a case in the middle: the index does not have all the columns required by the select, but can eliminate all rows.

The table created is:

create table demo1 as select generate_series n , 1 a , lpad('x',1000,'x') x from generate_series(1,10000);
SELECT 10000
create unique index demo1_n on demo1(n);
CREATE INDEX

Words I Don’t Use, Part 5: “Wait”

The fifth “word I do not use” is the Oracle technical term wait.

The Oracle Wait Interface

In 1991, Oracle Corporation released some of the most important software instrumentation of all time: the wait statistics that were implemented in Oracle 7.0. Here’s part of the story, in Juan Loaiza’s words, as told in Nørgaard et. al (2004), Oracle Insights: Tales of the Oak Table.

This stuff was developed because we were running a benchmark that we could not get to perform. We had spent several weeks trying to figure out what was happening with no success. The symptoms were clear—the system was mostly idle—we just couldn’t figure out why.

ODA X6 2S 2M 2L HA: Small Medium Large and High Availability

There are 4 models of Oracle Database Appliance with the new ODA X6 which is for the moment the latest ODA hardware version. One is similar to the previous X5-2 one, and 3 smaller ones known as ODA Lite. They are 1 year old already, here is a small recap of the differences and links to more detail.

System

The ODA X6 are composed with Oracle Server X6-2:

Join Elimination Bug

A few years ago a bug relating to join elimination showed up in a comment to a post I’d done about the need to keep on testing and learining. The bug was visible in version 11.2.0.2 and, with a script to replay it, I’d found that it had disappeared by 11.2.0.4.

Today I had a reason to rediscover the script, and decided to test it against 12.2.0.1 – and found that the bug was still present.

Here’s the model:

Latest Delphix Blog Post and Upcoming Webinars

In my latest blog post on the Delphix site, I continue my conversation with why DevOps is the next step for DBAs and how DBAs can embrace this next step in their evolution.

Installation of Rundeck with the Ansible plugin on Centos 7

This post shows you how to install Rundeck with the Ansible plugin on Centos 7. The installation is done with nginx as the web server and using SSL with a self signed certificate. Please read the Ansible installation script, and modify anything that should be different for your situation. You will be amazed how well readable the installation script is!

Rundeck is a web based user interface that allows you to run commands against a group of hosts. Rundeck has an ansible plugin. Using that plugin, it could perform the similar functionality as Ansible Tower (commercial product) or Semaphore (open source).

After a fresh installation of Centos 7, do the following as root:

Postgres vs. Oracle access paths VI – Index Scan

In the previous post my queries were still reading the indexed column only, from a table which had no modifications since the last vacuum, and then didn’t need to read table pages: it was Index Only Scan. However, we often need more columns than the ones that are in the index. Here is the Index Scan access path.