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March 2016

Also Extensions Created Because of SQL Plan Directives Can Invalidate Packages – Take Two

In a previous post I described a situation where the creation of an extension, independently of whether it’s carried out manually by a person or automatically by the database engine, can lead to the invalidation of PL/SQL objects. In this second post on that subject, I describe, with the help of an example (I love examples!) based on the extension_invalidate_pkg_remote.sql script, what can happen when the table on which the extension is created is stored in a remote database.

Let’s start by creating the required objects. Notice that all objects are local but, because the package body references the table through a database link that points to the very same schema owning all other objects, the database engine considers it a remote table.

Is SLOB AWR Generation Really, Really, Really Slow on Oracle Database 11.2.0.4? Yes, Unless…

If you are testing SLOB against 11.2.0.4 and find that the AWR report generation phase of runit.sh is taking an inordinate amount of time (e.g., more than 10 seconds) then please be aware that, in the SLOB/awr subdirectory, there is a remedy script rightly called 11204-awr-stall-fix.sql.

Simply execute this script when connected to the instance with sysdba privilege and the problem will be solved. 

Wrong Results

Just in – a post on the Oracle-L mailing lists asks: “Is it a bug if a query returns one answer if you hint a full tablescan and another if you hint an indexed access path?” And my answer is, I think: “Not necessarily”:


SQL> select /*+ full(pt_range)  */ n2 from pt_range where n1 = 1 and n2 = 1;

        N2
----------
         1
SQL> select /*+ index(pt_range pt_i1) */ n2 from pt_range where n1 = 1 and n2 = 1;

        N2
----------
         1
         1

The index is NOT corrupt.

Can The Public Cloud Meet the Needs of Your Enterprise Applications?

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Any applications your company runs on premise can also be run in the public cloud. But does that mean they should be?

While the cloud offers well-documented benefits of flexibility, scalability, and cost efficiency, some applications — and especially business-critical enterprise applications — have specific characteristics that can make them tricky to move into a public cloud environment.

That’s not to say you shouldn’t consider the cloud as an option, but you should be aware of the following enterprise application needs before you make any migration decisions:

1. Highly customized infrastructure

EM13c DBaaS, Part 2, Thin Clone Issues

I’ve been working on a test environment consisting of multiple containers in a really cool little setup.

Oracle Cloud – Managing the Database as a Service Cloud

So I am not working in the Public Cloud for a week and last night…

OUG Ireland 2016 – Summary

oug-ireland-2016

The day started at 05:00. I lay in the bath for 20 minutes in denial, wondering how I would manage to stay awake for the day. I’ve been ill for ages, so I felt like I was running on empty anyway. Once I had managed to drag myself out of the bath and get dressed, I picked up my laptop and took a taxi to the airport.

The taxi to the airport was smooth enough. I was already checked in and had no bags to drop off, so I went straight for the security and was greeted by the biggest queue I had ever seen at Birmingham airport. To all those people that laugh at me getting to the airport 2+ hours before a short flight like this I say, “Better to be safe than sorry!”

Loss Aversion and the Setting of DB_BLOCK_CHECKSUM

Within Accenture Enkitec Group, we have recently been discussing the Oracle db_block_checksum parameter and how difficult it is to get clients to set it to a safer setting.

Clients are always concerned about the performance impact of features like this. Several years ago, I met a lot of people who had—in response to some expensive advice with which I strongly disagreed—turned off redo logging with an underscore parameter. The performance they would get from doing this would set the expectation level in their mind, which would cause them to resist (strenuously!) any notion of switching this [now horribly expensive] logging back on. Of course, it makes you wish that it had never even been a parameter.

TOP-N histograms on 12c

I had an interesting question on AskTom today, with a nicely provided test case !!!,  so I thought I’d share it here with some additional commentary.