I’ve just noticed that the new HTML MOS introduced a nice addition to the old ORA-600/ORA-7445 Error Look-up Tool: now there is a new ORA-600 Troubleshooting Tool (if the link is not opened automatically for you try refreshing the page with F5 – works for me in Chrome). Within a few minutes it allows you [...]
Thanks to everyone for spreading the link and participating in the poll on statistics. As it was pointed out in the comments, the poll isn’t very specific, I know. My point was to get an idea how many people use the defaults (I considered Oracle version 11g) for stats collection, how many do a very [...]
This is a short note on the topic of information exchange. I use OraNA.info to get up-to-date technology news. This is a blog aggregator I’ve tried first and have been using it since then, which is 3-4 years I guess. It’s great and I’d like to use this opportunity to say Thank You to Eddie [...]
Here is a poll prompted by today twitter talks on the default METHOD_OPT value (which is ‘for all columns size auto’ since 10g) and automatic statistics gathering job (auto-task since 11g). CBO development team suggests to use the default job to gather statistics with default options. Do you use the job exactly this way with [...]
The post reminded me of my own fail happened several months ago.
I’ve a level 5 Statspack report from a real production 11.2.0.2 database with the following Top 5 Timed events section: The complete report (without SQL and several other sections) is here. Can you explain what & why is wrong in this Top? I must admit I don’t have the definitive answer (probably yet), but I [...]
If you you want to get an idea how some feature may be implemented by Oracle, then you ought to have a look for patents. Here are several examples I find quite interesting and containing valuable information: Method and apparatus for reapplying changes to a database – gives you an algorithm how Oracle optimizes recovery [...]
In the previous post I wrote about strangely behaving V$SQL. For some reason there were duplicate rows leading to wrong results issue when running DBMS_XPLAN.DISPLAY_CURSOR for a particular child cursor. I tried to reproduce the issue using simple test case – and it was reproduced.
The column is there for a long time – even 9i documentation have it. I’ve never thought about it until today when I caought something extraordinary on 11.2.0.3 instance.
February 24, 2012 – 18:29
Daylight Saving Time in Russia has been changed last year. Oracle published a FAQ on the support site about this: Russia abandons DST in 2011 – Impact on Oracle RDBMS [ID 1335999.1].
February 21, 2012 – 23:15
I like Load profile section of Statspack or AWR reports (who doesn’t). It’s short and gives a brief understanding of what kind of work a database does. But what if you don’t have an access to Statspack or AWR but still want to see something similar? It’s possible to use V$SYSMETRIC to get this numbers [...]
February 21, 2012 – 12:55
It’s been too long from a previous wish for Oracle. While reading a MOS updated articles (in a new HTML interface which looks nice, much better than flash-based introduction) I’ve seen this document that made me write this blog post. As you know, Oracle has V$SQL_SHARED_CURSOR view that helps to understand why a particular child [...]
February 15, 2012 – 21:30
On February 10th I was in Saint Petersburg on a seminar organized by Russian Oracle User Group. Actually, it was mostly prepared by company called Devexperts. Seminar took place in their office, with most presentations done by their people.
December 14, 2011 – 18:45
In our application we extensively use a function-based index on an important table. Couple of days ago I’ve seen an interesting issue associated with this FBI, view and a GROUP BY query. I have to say I don’t have an explanation what exactly it is and how I should call it properly, hence just “trouble” [...]
As Martin I had a pleasure to “unofficially” review Jonathan’s latest book, Oracle Core. It was my first experience in the area of printed content. If you want to know little bit more how the process went, my opinion on the book and what to expect from it – I’ll try to cover these points [...]
November 28, 2011 – 21:15
Recent Charles Hooper’s post on the topic of Recycle bin (which is, BTW, documented behavior) reminded me of an issue with that functionality I’ve seen recently. The problem was a single-row INSERT INTO table VALUES () statement was hanging for more than an hour burning CPU.
November 24, 2011 – 22:09
Recently I did an investigation of an ORA-04031 which happens almost regularly on a 10.2.0.4 Oracle database server with 9G of memory allocated to shared pool and disabled Automatic Shared Memory Management (sga_target=0). The problem query is a report that is a very big SQL query – more than 200K of plain text. The exact [...]
November 21, 2011 – 17:46
And you should remember that. Here is a nice example how Cost Based Optimizer can miss an obvious option (which is available to human eye and Oracle run-time with a hint) while searching for the best plan. CBO simply doesn’t consider Index Skip Scan with constant ‘in list’ predicates in the query, although it costs [...]
November 17, 2011 – 21:30
I planned to write on this for quite some time, but failed to do so. Sorry about that. Today I finally got time and desire to describe a situation from the title. It was observed on an Oracle 9.2.0.8 running Solaris SPARC; manifested itself as a severe CPU burning at 100% utilization with ‘latch free’ [...]
Here is a nice example of what Oracle 11.2.0.2 is able to do with a subquery inside an expression. It can unnest it – that is a new 11.2.0.2 feature of the transformation part of the CBO.
