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July 2018

Easy way to create large demo-tables in #Exasol and #Oracle

https://uhesse.files.wordpress.com/2015/10/helps.png?w=600&h=558 600w, https://uhesse.files.wordpress.com/2015/10/

Announcement: Venue Confirmed For Upcoming Brussels “Oracle Indexing Internals and Best Practices” Seminar

I can finally confirm the venue for my upcoming “Oracle Indexing Internals and Best Practices” seminar in beautiful Brussels, Belgium running on 27-28 September 2018. The venue will be the Regus Brussels City Centre Training Rooms Facility, Avenue Louise / Louizalaan 65, Stephanie Square, 1050, Brussels. Note: This will be the last public seminar I’ll run […]

Searching in Oracle Database documentation

Just a quick heads up with something I see from time to time in Chrome (but not in Firefox or any other browser).

Occasionally when doing a search, the results are not limited as per my criteria.  For example, if I am searching for information about Spatial in the Licensing Guide:

image

then when I click the Search button, the results might come back with a far broader search range:

Which Privileges Are Required to Use the ADWC Service Console?

The Autonomous Data Warehouse Cloud (ADWC) service provides a Service Console that can be used to monitor the service activity and to carry out a small number of administration tasks (e.g. changing some resource management rules).

The documentation specifically says to use the ADMIN user to login. But, actually, any unlocked database user having the CREATE SESSION privilege can be used to login. This is not only useful, but, in my opinion, necessary. In fact, developers should be able to see the service activity without knowing the password of the ADMIN user.

Rebuilding Indexes: Danger With Clustering Factor Calculation (Chilly Down)

Let me start by saying if you don’t already following Jonathan Lewis’s excellent Oracle blog, do yourself a favour. In a recent article, Jonathan highlighted a danger with rebuilding indexes (or indeed creating an index) when used in relation to collecting index statistics with the TABLE_CACHED_BLOCKS preference. I’ve discussed the importance of the TABLE_CACHED_BLOCKS statistics […]

#Exasol Cluster Architecture

This article gives a more detailed view on the Exasol Cluster Architecture. A high level view is provided here.

Exasol Cluster Nodes: Hardware

An Exasol Cluster is built with commodity Intel servers without any particular expensive components. SAS hard drives and Ethernet Cards are sufficient. Especially there is no need for an additional storage layer like a SAN.

See here for a list of Exasol Certified Servers.

Google Cloud Spanner – no decimal numeric data types

By Franck Pachot

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Google Cloud Spanner is a distributed relational database focused on scalability without compromising consistency and integrity. It is available only as a managed service in Google Cloud. Basically, the idea is to keep the scalability advantages of NoSQL database (like Bigtable) but adding transactions, relational tables, SQL, structured data,… as in the relational databases we love for decades.
The commercial pitch includes all the NoSQL buzzwords, with the addition of the legacy properties of SQL databases:
Cloud Spanner is a fully managed, mission-critical, relational database service that offers transactional consistency at global scale, schemas, SQL (ANSI 2011 with extensions), and automatic, synchronous replication for high availability.
Here I’m testing something that is not mentioned, but is taken for granted with all SQL databases: the ability to add numbers without erroneous arithmetic results.

Direct IOT

A recent (automatic ?) tweet from Connor McDonald highlighted an article he’d written a couple of years ago about an enhancement introduced in 12c that allowed for direct path inserts to index organized tables (IOTs). The article included a demonstration seemed to suggest that direct path loads to IOTs were of no benefit, and ended with the comment (which could be applied to any Oracle feature): “Direct mode insert is a very cool facility, but it doesn’t mean that it’s going to be the best option in every situation.”

Drilling down the pgSentinel Active Session History

By Franck Pachot

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In pgSentinel: the sampling approach for PostgreSQL I mentioned that one of the advantages of the ASH approach is the ability to drill down from an overview of the database activity, down to the details where we can do some tuning. The idea is to always focus on the components which are relevant to our tuning goal:

strace the current Oracle session process

Here is my way to trace system calls from the current session process.
This must not be done in production.
An strace.log file will be generated with system calls

connect / as sysdba
column spid new_value pid
select spid from v$process join v$session on v$session.paddr=v$process.addr where sid=sys_context('userenv','sid');
column spid clear
define bg=&:
host strace -fy -p &pid -o strace.log &bg
select * from v$osstat;
disconnect

Originally posted on Twitter, but improved here

https://twitter.com/FranckPachot/status/969898128030695424