Bulk collect workaround for memory bug

A coworker passed a test script on to me that was failing with the following memory error:

ORA-04030: out of process memory when trying to allocate 4088 bytes (PLS CGA hp,pdzgM64_New_Link)

The error occurred when initializing a PL/SQL table variable with 7500 objects. Here is my sanitized version of the code:

CREATE OR REPLACE TYPE ARRAY_ELEMENT
AS
  OBJECT
  (
    n1 NUMBER,
    n2 NUMBER,
    n3 NUMBER,
    n4 NUMBER );
/

CREATE OR REPLACE TYPE MY_ARRAY
IS
   (more...)

Finished Mathematics for Computer Science class

Today I finally finished the Mathematics for Computer Science class that I have worked on since December. For the last year or two I have wanted to do some general Computer Science study in my free time that is not directly related to my work. I documented a lot of this journey in an earlier blog post.

The math class is on MIT’s OpenCourseWare (OCW) web site. It was an undergraduate semester class and I spent about (more...)

Trying VirtualBox

I have been using  VMware Player to build test virtual machines on my laptop with an external drive for some time now. I used to use the free VMware Server. My test VMs weren’t fast because of the slow disk drive but they were good enough to run small Linux VMs to evaluate software. I also had one VM to do some C hacking of the game Nethack for fun. I got a lot of good (more...)

Modified IO CPU+IO Elapsed Graph (sigscpuio)

Still tweaking my Python based Oracle database performance tuning graphs.

I kind of like this new version of my “sigscpuio” graph:

blogiopluscp2u

The earlier version plotted IO, CPU, and Elapsed time summed over a group of force matching signatures. It showed the components of the time spent by the SQL statements represented by those signatures. But the IO and CPU lines overlapped and you really could not tell how the elapsed time related to IO and (more...)

Graph frequently executed SQL by FORCE_MATCHING_SIGNATURE

I made a new graph in my PythonDBAGraphs program. Here is an example with real data but the database name blanked out:

sql_matching_group_of_signatures_blog

My graphs are all sized for 1920 x 1080 monitors so I can see all the detail in the lines using my entire screen. The idea for this graph is to show how the performance of the queries that matter to the users changes as we add more load and data to this (more...)

Understanding query slowness after platform change

We are moving a production database from 10.2 Oracle on HP-UX 64 bit Itanium to 11.2 Oracle on Linux on 64 bit Intel x86. So, we are upgrading the database software from 10.2 to 11.2. We are also changing endianness from Itanium’s byte order to that of Intel’s x86-64 processors. Also, my tests have shown that the new processors are about twice as fast as the older Itanium CPUs.

Two SQL (more...)

Comparing Common Queries Between Test and Production

The developers complained that their test database was so much slower than production that they could not use it to really test whether their batch processes would run fast enough when migrated to production. They did not give me any particular queries to check. Instead they said that the system was generally too slow. So, I went through a process to find SQL statements that they had run in test and that normally run in production (more...)

Jonathan Lewis

I am finally getting around to finishing my four-part blog series on people who have had the most influence on my Oracle performance tuning work. The previous three people were Craig ShallahamerDon Burleson, and Cary Millsap. The last person is Jonathan Lewis. These four people, listed and blogged about in chronological order, had the most influence on my understanding of how to do Oracle database performance tuning. There are many other great (more...)

Log file parallel write wait graph

I got a chance to use my onewait Python based graph to help with a performance problem. I’m looking at slow write time from the log writer on Thursday mornings. Here is the graph with the database name erased:

log_file_parallel_write_waits

We are still trying to track down the source of the problem but there seems to be a backup on another system that runs at times that correspond to the spike in log file parallel write (more...)

Python DBA Graphs Github Repository

I decided to get rid of the Github repository that I had experimented with and to create a new one. The old one had a dump of all my SQL scripts but without any documentation. But, I have updated my Python graphing scripts a bit at a time and have had some recent value from these scripts in my Oracle database tuning work. So, I created a Github repository called PythonDBAGraphs. I think it will (more...)