December 2014

Oracle database operating system memory allocation management for PGA – part 3: Oracle 11.2.0.4 and AMM: Quiz

This is a series of blogposts on how the Oracle database makes use of PGA. Earlier posts can be found here (PGA limiting for Oracle 12) and here (PGA limiting for Oracle 11.2).

Today a little wednesday fun: a quiz.

What do you think will happen in the following situation (leave a response as comment please!):

-Oracle Linux x86_64 6u6.
-Oracle database 11.2.0.4 PSU 4
-Oracle database (single instance) with the following parameter set: memory_target=1G. No other memory related parameters set.

SLOB 2.2 Not Generating AWR reports? Testing Large User Counts With Think Time? Think Processes and SLOB_DEBUG.

I’ve gotten a lot of reports of folks branching out into SLOB 2.2 large user count testing with the SLOB 2.2 Think Time feature. I’m also getting reports that some of the same folks are not getting the resultant AWR reports one expects from a SLOB test.

If you are not getting your AWR reports there is the old issue I blogged about here (click here). That old issue was related to a Redhat bug.  However, if you have addressed that problem, and still are not getting your AWR reports from large user count testing, it might be something as simple as the processes initialization parameter. After all, most folks have been accustomed to generating massive amounts of physical I/O with SLOB at low session counts.

RMOUG Training Days 2015!

OK, Oracle EM hat off, RMOUG Training Days hat on! :)

Oracle database operating system memory allocation management for PGA – part 2: Oracle 11.2

This is the second part of a series of blogpost on Oracle database PGA usage. See the first part here. The first part described SGA and PGA usage, their distinction (SGA being static, PGA being variable), the problem (no limitation for PGA allocations outside of sort, hash and bitmap memory), a resolution for Oracle 12 (PGA_AGGREGATE_LIMIT), and some specifics about that (it doesn’t look like a very hard limit).

But this leaves out Oracle version 11.2. In reality, the vast majority of the database that I deal with at the time of writing is at version 11.2, and my guess is that this is not just the databases I deal with, but a general tendency. This could change in the coming time with the desupport of Oracle 11.2, however I suspect the installed base of Oracle version 12 to increase gradually and smoothly instead of in a big bang.

Adventures in RAC: gc buffer busy acquire and release

It seems that I’m getting more and more drawn into the world of performance analysis, and since I sometimes tend to forget things I need to write them down. I almost enjoy the “getting there” more than ultimately solving the problem. You pick up quite a few things on the way.

This environment is Exadata 12.1.1.1.1/Oracle 12.1.0.2 but as with so many things the fact that the database is on Exadata shouldn’t matter.

So here is one of these posts, this time I’m writing up what I saw related to GC Buffer Busy Acquire.

gc buffer busy acquire?

Whenever I see a wait event I haven’t dealt with extensively in the past I try to provoke behaviour to study it more closely. But first you need to know the event’s meaning. One option is to check v$event_name:

SLOB Data Loading Case Studies – Part II. SLOB 2.2 For High-Bandwidth Data Loading.

BLOG UPDATE 2015.07.24: For all testing recipes please visit the SLOB Recipes section of kevinclosson.net/slob

This is Part II in a series. Part I can be found here (click here). Part I in the series covered a very simple case of SLOB data loading. This installment is aimed at how one can use SLOB as a platform test for a unique blend of concurrent, high-bandwidth data loading, index creation and CBO statistics gathering.

Put SLOB On The Box – Not In a Box

As a reminder, the latest SLOB kit is always available here: kevinclosson.net/slob .

Oracle database operating system memory allocation management for PGA

This post is about memory management on the operating system level of an Oracle database. The first question that might pop in your head is: isn’t this a solved problem? The answer is: yes, if you use Oracle’s AMM (Automatic Memory Management) feature, which let’s you set a limit for the Oracle datababase’s two main memory area’s: SGA and PGA. But in my opinion any serious, real life, usage of an Oracle database on Linux will be (severely) constrained in performance because of the lack of huge pages with AMM, and I personally witnessed very strange behaviour and process deaths with the AMM feature and high demand for memory.

Day 3+ of UKOUG Tech 14

Sorry it’s taken a couple of days to finish off this series of blog posts on UKOUG Tech 14. I had expected to get some time on the trip back to write this, but as you’ll see if you keep reading, that really didn’t happen. So let’s go back to Day 3 of the conference.

ORA-4068 and CONSTANT keyword…good and bad

Anyone that has ever coded PLSQL will be familiar with the error ORA-4068, where you had some state persisted in a session due to a package variable, and then when you change the package, the state is cleared along with an ORA-4068.  Here’s a quick example:

 

Session 1 

SQL> create or replace
  2  package PKG is
  3    procedure P;
  4  end;
  5  /

Package created.

SQL> create or replace
  2  package body PKG is
  3      my_global int := 10;
  4    procedure P is
  5    begin
  6       null;
  7    end;
  8  end;
  9  /

Package body created.

Session 2 

SQL> exec pkg.p

PL/SQL procedure successfully completed.

Session 1

Now we change the package… In this case, I’ve just changed the value of the global

EM12c Management Agent, OutOfMemoryError and Ulimits

While enjoying the lovely Liverpool, UK weather at Tech14 with UKOUG, (just kidding about that weather part and apologies to the poor guy who asked me the origin of “Kevlar” which in my pained, sleep-deprived state I answered with a strange, long-winded response….