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cursor: pin S waits, sporadic CPU spikes and systematic troubleshooting

I recently consulted one big telecom and helped to solve their sporadic performance problem which had troubled them for some months. It was an interesting case as it happened in the Oracle / OS touchpoint and it was a product of multiple “root causes”, not just one, an early Oracle mutex design bug and a Unix scheduling issue – that’s why it had been hard to resolve earlier despite multiple SRs opened etc.

Martin Meyer, their lead DBA, posted some info about the problem and technical details, so before going on, you should read his blog entry and read my comments below after this:

Problem:

So, the problem was, that occasionally the critical application transactions which should have taken very short time in the database (<1s), took 10-15 seconds or even longer and timed out.

Symptoms:

KGH: NO ACCESS – Buffer cache inside streams pool too!

Some time ago I wrote that since Oracle 10.2, some of the buffer cache can physically reside within shared pool granules.

I just noticed this in an 11.2 instance:

ORA-01719 is partially relaxed

You most likely have seen this error before: ORA-01719: outer join operator (+) not allowed in operand of OR or IN Cause: An outer join appears in an or clause. Action: If A and B are predicates, to get the effect of (A(+) or B), try (select where (A(+) and not B)) union all (select [...]

This Is A VERY Boring Blog!

I’ve been stranded in Europe for 4 days and the situation persists!  Needless to say I haven’t been thinking that much about blogging I do have a post nearly ready to go about booting 4s48c Opteron 6100 systems with _enable_NUMA_support set to TRUE. There are some caveats, and some very significant benefits as well. I’ll [...]

5th Planboard DBA Symposium: Registration now open

On June 8 Planboard will run her 5th Dutch DBA Symposium and the registration is now open. This “for Dutch DBA’s, by Dutch DBA’s” symposium has become the place to be for the serious DBA who wants to share his or her knowledge with other DBA’s in an open environment with plenty of networking time […]

The Core Performance Fundamentals Of Oracle Data Warehousing – Parallel Execution

[back to Introduction] Leveraging Oracle’s Parallel Execution (PX) in your Oracle data warehouse is probably the most important feature/technology one can use to speed up operations on large data sets.  PX is not, however, “go fast” magic pixi dust for any old operation (if thats what you think, you probably don’t understand the parallel computing paradigm). With Oracle PX, a large task is broken up into smaller parts, sub-tasks if you will, and each sub-task is then worked on in parallel.  The goal of Oracle PX: divide and conquer.  This allows a significant amount of hardware resources to be engaged in solving a single problem and is what allows the Oracle database to scale up and out when working with large data sets. I though I’d touch on some basics and add my observations but this is by far not an exhaustive write up on Oracle’s Parallel Execution.  There is an entire chapter in the Oracle Database documentation on PX as well as several white papers.  I’ve listed all these in the Resources section at the bottom of this post.  Read them, but as always, feel free to post questions/comments here.  Discussion adds great value. A Basic Example of Parallel Execution [...]

When column name matters

There’s a thread on the OTN forum with a case of amusing behavior of the 11.2.0.1 JDBC driver: it fails to detect properly all bind variables in an SQL statement referencing column named NORDER. WTF?! PS. 1) Oracle’s SSO is actually Multi Sign-On because I have two accounts (one for OTN forums and one for [...]

NL join (ordered)

Some time ago there was a thread on the SQL.ru forum where user has asked the never-ending question “why CBO is doing this?”. The problem was a simple count(*) of parent-child tables join with no FK constraint was executed in very strange way: via NESTED LOOPS using child as a driving table. Here is a [...]

Funny Developer Tricks - first_rows(999999999)

I ran across a funny SQL statement recently (funny strange, not funny ha ha - well actually funny ha ha too I guess). It had a first_rows hint like so:

An Evening with Oracle Database Security Expert: Pete Finnigan


AMIS Technology School is proud to present, in collaboration with Miracle Benelux Masterclasses:

Miracle Benelux and Pete Finnigan agreed to do an extra special on the AMIS premises the evening just before Pete’s 2 day Masterclass in Utrecht will start (for the 2 day Masterclass agenda, see also the following URL). During this AMIS Query, besides the free food and normal standard setup of such an AMIS Query Event, Pete will have a presentation on Oracle security and there will be a lot of room of informal discussions during and after this session. There is still some room if you would like to learn from one of the best on Oracle database security.

Pete Finnigan

More details on those masterclasses can be found on the Miracle Benelux site. Hopefully this will be the first of series… More details about this event will follow shortly.