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September 2013

Clusterware and listener management gotcha in 11.2

I have come across an interesting situation recently and thought it was worth blogging about. My friend Doug Burns might like it, it has to do with consolidation.

Background

I have seen quite a few sites in my career where the separation (of duties/listeners/disk space/log destinations) was paramount-and for good reason! In fact Oracle propagate it as well as a quick search with your favourite search engine will show. In my example I came across a system that used different listeners per database, which is very common and prevents users from “accidentally” connecting to the wrong system. If you are using such a setup please read on. If you are not using Oracle Restart/Clusterware/RAC then this is not immediately relevant to your Oracle estate.

Webinar

Last chance to book a seat for tomorrow’s 90 minute session(s) on Selectivity:

Block Change Tracking setup and overhead


tea plantation

For everything you ever wanted to know about Block Change Tracking (BCT) and were afraid to ask, check out the awesome presentation from Alex Gorbechev

EM12c Enterprise Monitoring, Part V “Warning Management”

This is Part IV in a multi-part series, demonstrating how to take EM12c from out of the box to enterprise level.  

End of WIT and the Workplace Posts

This is my last WIT post on the challenges on women in the workplace.  The truth of the matter is, its just too difficult to write about what women are facing in the workplace without a large amount of risk.

Data Control


Video of webinar given on Data Control by myself and James Murtagh of Red Gate


 

Screen Shot 2013-09-05 at 5.26.06 PM

Parallel Execution

While checking out potential scalability threats recently on a client system, I was directed to a time-critical task that was currently executing the same PL/SQL procedure 16 times (with different parameters) between 6:00 and 7:00 am; as the system went through its next phase of expansion the number of executions of this procedure was likely to grow. An interesting detail, though, was that nothing else was going on while the task was running so the machine (which had 6 cores) was running at 16% CPU.

An obvious strategy for handling the required growth target was to make sure that four (possibly 5) copies of the procedure were allowed to run concurrently. Fortunately the different executions were completely independent of each other and didn’t interfere with each other’s data, so the solution simply required a mechanism to control the parallelism. Conveniently 11gR2 gave us one.

RAC Internals: cached sequences and 12c

Introduction

I blogged about DFS lock handle contention in an earlier blog entry. SV resources in Global Resource Directory (GRD) is used to maintain the cached sequence values. I will further probe the internal mechanics involved in the cached sequences. I will also discuss minor changes in the resource names to support pluggable databases (version 12c).

SV resources

Let’s create an ordered sequence in rs schema and then query values from the sequence few times.

create sequence rs.test_seq order cache 100;
select rs.test_seq.nextval from dual; -- repeated a few times.
...
/
21

Sequence values are permanently stored in the seq$ dictionary table. Cached sequence values are maintained in SV resources in GRD and SV resource names follows the naming convention to include object_id of the sequence. I will generate a string using a small helper script and we will use that resource name to search in the GRD.

OOW + Delphix

There’s going to be a day of Delphix activity at OpenWorld – with a Customer Forum being held in the B Restaurant (above Moscone North) on Tuesday 24th September. I’ll be joining them from 2:00 pm to 3:00 pm on a panel session chaired by Adam Leventhal. The starting topic will be: “Bridging IT and Business: Demonstrating the Value of Delphix”.

Captain Support and Windows 8…

Captain Support was getting pretty sick of supporting the crappy old laptops his brother and mother were using, so he selfishly bought them 2 shiny new laptops to make his own life easier. The only slight flaw in the plan was they came with Windows 8. Although Captain Support had some previous experience of Windows 8 (Developer Preview, Consumer Preview, Windows Blue beta), he was a little nervous about unleashing it on his unsuspecting family members…