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IOUG Collaborate 2017

I have a few presentations scheduled in IOUG Collaborate 2017, Las Vegas.

1. Session: 621: RAC Clusterware internals
**Date/time: Mon, Apr 03, 2017 (01:30 PM – 02:30 PM) : Jasmine A

2. Session: RAC cache fusion internals. ( OakTable track )
**Date/time: Wed, Apr 05, 2017 (09:45 AM – 10:45 AM) Room: South Seas C

3. Session: 479: An in-depth review of ASM and internals
**Date/time: Wed, Apr 05, 2017 (02:45 PM – 03:45 PM) : Palm B

Presentation files ( Updated after the presentations).

Thank you for coming to my presentation(s).

RMOUG Training days 2017

I will be speaking about the following topics in Rocky Mountain Oracle User group Training days (RMOUG, Denver) February 7-9, 2017.

Come to my presentations and say Hi to me </p />

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SLOB 2.3 Data Loading Failed? Here’s a Quick Diagnosis Tip.

The upcoming SLOB 2.4 release will bring improved data loading error handling. While still using SLOB 2.3, users can suffer data loading failures that may appear–on the surface–to be difficult to diagnose.

Before I continue, I should point out that the most common data loading failure with SLOB in pre-2.4 releases is the concurrent data loading phase suffering lack of sort space in TEMP. To that end, here is an example of a SLOB 2.3 data loading failure due to shortage of TEMP space. Please notice the grep command (in Figure 2 below) one should use to begin diagnosis of any SLOB data loading failure:

CPU profiling using perf utility in Linux

After reading my blog entry about a performance issue due to excessive HCC decompression ( Accessing HCC compressed objects using index access path, a reader asked me about the CPU profiling method I mentioned in that blog entry. I started responding to that comment, and realized that the response was too big for a comment. So, in this blog entry, I will cover basics of the CPU profiling in Linux. Other platform provides similar utilities, for example, Solaris provides an utility dtrace.

Tool Box

Accessing HCC compressed objects using an index


I came across another strange SQL performance issue: Problem was that a SQL statement was running for about 3+ hours in an User Acceptance (UA) database, compared to 1 hour in a development database. I ruled out usual culprits such as statistics, degree of parallelism etc. Reviewing the SQL Monitor output posted below, you can see that the SQL statement has already done 6 Billion buffer gets and steps 21 through 27 were executed 3 Billion times so far.

Statistics and execution plan

library cache lock on BUILD$ object

I was testing an application performance in 12c, and one job was constantly running slower than 11g. This post is to detail the steps. I hope the steps would be useful if you encounter similar issue.


In an one hour period, over 90% of the DB time spent on waiting for library cache lock waits. Upon investigation, one statement was suffering from excessive waits for ‘library cache lock’ event. We recreated the problem and investigated it further to understand the issue.

Following is the output of wait_details_rac.sql script (that I will upload here) and there are many PX query servers are waiting for ‘library cache lock’ wait event.


Over the last many years, some of you have invited me to attend conferences in India, and talk about Oracle RAC and performance. I have not had an opportunity to make it to conferences in India, until now </p />

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OOUG RAC day presentation files and scripts

Thanks for coming to my presentations in RAC day at Dublin, Ohio. Please find the presentation files below. Hopefully, I will get video files and upload that here too.

OOUG presentation files and scripts

md5 checksum of the zip file is:


RAC day with Ohio Oracle User Group

I will be talking about RAC and performance in-depth, with lots of demos, in a RAC day training with Ohio Oracle User group on Nov 16,2015 Monday. Venue for the presentation is Dublin, Ohio.

Agenda for the day:

08:00a – 09:00: Registration / Breakfast

09:00a – 09:15: Announcements -Introduction of the speaker

09:15a – 10:30: Underpinning for Oracle RAC and Clusterware

10:30a – 10:45: Break

10:45a – 11:45: RAC cache fusion internals

11:45a – 01:00: Lunch

01:00p – 02:00: RAC Performance tuning Part 1 – Wait events and object tuning

02:00p – 02:15: Break

02:15p – 03:30: RAC performance tuning Part 2 – locks, library cache locks etc.

03:30p – 03:45: Member Announcements, Gift Drawings

Please RSVP to the co-ordinators so that you will have a seat </p />

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NYOUG Session: Latches Demystified

Thank you all those who came to attend my session on demystifying latches at New York Oracle Users Group in Manhattan. I hope you found the session useful and enjoyable.