oracle performance

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.

A quick note, Expert Oracle RAC book co-written by me is available now: Expert Oracle RAC 12c. I have written about 6 chapters covering the RAC internals that you may want to learn I even managed to discuss the network internals in deep, after all, network is one of the most important component of a RAC cluster.

My next Embarcadero sponsored webinar will be on May 14 and is entitled Using Optimizer Hints for Oracle Performance Tuning.

Register now!

Thanks to everyone who attended my webinar and thanks to Embarcadero (@DBPowerStudio) for hosting it. The presentation and scripts can be downloaded from the following links:

Presentation (PDF)
Scripts (ZIP)

It's webinar time again! On March 26, Embarcadero will once again provide sponsorship for my webinar entitled "Back to the Future: Mining AWR Data for Oracle SQL Performance".

Abstract

Thanks everyone who attended the 3rd segment of my 3-part DBA Performance webinar series. I enjoyed delivering them and hope you found them informative and useful.

You can find the recording here and the presentation slide deck here.

There were two SQL statements in the deck that were used to produce execution plan output (either using dbms_xplan.display_cursor or dbms_sqltune.report_sql_monitor). So you won't have to type them if you want to use them, here they are:

-- SQL to produce execution plan using dbms_xplan.display_cursor

Join me on Wednesday, September 26 as I present a webinar entitled "Making Impactful Performance Changes". This is the final segment in the 3-part DBA Performance Series sponsored by Embarcadero. Register even if you can't make it and you'll get an email with the link to the webcast video after it's over.

In this webinar, I'll cover

• Common ways to rewrite SQL that make it perform better and more consistently
• How and when to add or modify indexes 
• How and when the SQL Tuning Advisor helps you and when it doesn't

During last week's webinar, there were several questions that I did not have a chance to answer so I wanted to follow-up by answering those questions here. I also wanted to provide links to previous webinar recordings as many people had asked where to find them.

Webinar Recordings
Best Practices for Developing Optimally Performing SQL

Diagnosing SQL Performance Problems (Part 1 of 3 part series)

Thanks again to everyone who attended part 2 of my Oracle SQL Performance webinar series entitled Making SQL Performance Solutions Stick. Embarcadero will be posting the recording within the next few days. In the meantime, I have uploaded the slides and scripts.

Thanks again and don't forget about the final installment in the series coming next month on September 29 entitled Making Impactful Performance Changes.

I hope to see you then!

There are many questions from few of my clients about asmlib support in RHEL6, as they are gearing up to upgrade the database servers to RHEL6. There is a controversy about asmlib support in RHEL6.  As usual, I will only discuss technical details in this blog entry.

ASMLIB is applicable only to Linux platform and does not apply to any other platform.

Now, you might ask why bother and why not just use OEL and UK? Well, not every Linux server is used as a database server. In a typical company, there are hundreds of Linux servers and just few percent of those servers are used as Database servers. Linux system administrators prefer to keep one flavor of Linux distribution for management ease and so, asking clients to change the distribution from RHEL to OEL or OEL to RHEL is always not a viable option.

Do you need to use ASMLIB in Linux?