Presentation material & E-learning videos – In-Memory Column Store Workshop with Maria Colgan

You can now download and have another look at the presentations used during the In-Memory…

Visualizing Statspack “Average Active Sessions” in SQL Developer

This is the second post in my mini-series on leveraging SQL Developer Reports for DBA tasks, today with visualizing Average Active Sessions (AAS). In this article I’ll cover What AAS is and how to interpret it How to build a basic line graph in SQL Developer How to extend the graph with detailed child reports (Time […]

Instrumenting OBIEE Database Connections For Improved Performance Diagnostics

Nearly four years ago I wrote a blog post entitled “Instrumenting OBIEE – The Final Chapter”. With hindsight, that title suffix (“The Final Chapter”) may have been a tad presumptuous and naïve of me (or perhaps I can just pretend to be ironic now and go for a five-part-trilogy style approach…). Back then OBIEE 11g had only just been released (who remembers 11.1.1.3 in all its buggy-glory?), and in (more...)

Visualizing Statspack Performance Data in SQL Developer

If you run Oracle Standard Edition or haven’t licenced Diagnostics Pack for Enterprise Edition, then you don’t have AWR and ASH Data available. This is when Statspack, the predecessor of AWR, comes in handy to keep a history of database performance metrics. But although Oracle still deliver Statspack with their recent DB releases (yes, even in […]

Extra-cost Option?


"Just because you have a choice, it doesn't mean that any of them 'has' to be right."
 Norton Juster, The Phantom Tollbooth 

In an Oracle forum that I frequent a user posted that he found cardinality values to be severely inflated when using an analytic function. This user posted an example that will be used here to demonstrate the problem. It will also be used to demonstrate another issue that can make this problem (more...)

An Introduction to Analysing ODI Runtime Data Through Elasticsearch and Kibana 4

An important part of working with ODI is analysing the performance when it runs, and identifying steps that might be inefficient as well as variations in runtime against a baseline trend. The Operator tool in ODI itself is great for digging down into individual sessions and load plan executions, but for broader analysis we need a different approach. We also need to make sure we keep the data available for trend analysis, as it’s often the (more...)

Tablespace growth history

Recently we had a tablespace space run out and ended up in an application failure.  I have questioned my DBA and he just plainly blamed the application team members who loaded large number records without a prior notice.  A convincing answer, but you can’t really fool Oracle.

Oracle introduced a new DBA_TABLESPACE_USAGE_METRICS view from 10g onwards to report the space usage with in a tablespace.  I created a new tablespace and immediately (more...)

Invoking REST Service from Oracle ACM Java Activity

In this post I will show you, how to call REST service from ACM Java activity class method. This could be useful in the situations, when you would like to have programmatic ACM activity integrated with REST service data. We could access ACM payload data from within the method overriden in the class implementing Case Activity Callback.

ACM activity implemented on top of Java class, contains the same properties and configuration as the regular one. (more...)

x$bh and consistency

Oracle caches the data blocks in buffer cache in various modes depends on the block usage.  As per the Oracle documentation it can CR (Consistent mode – reads), XCUR (Current mode – updates), FREE etc.   I understand and other heard saying – whenever a block READs into memory will be in CR mode while if the block is fetching for UPDATE it will be in XCUR mode so that sessions can apply the (more...)

In Memory XML Performance (XVM)

I wouldn’t believe the bad XMLType performance statement given stated in Martin Preiss’ blog post,…

Developer Interview (#DI15) with Niko Köbler (@dasniko) Java EE and Node.js Performance

Developer interview Friday. Today it is my pleasure to welcome Niko Köbler (@dasniko). We meet a couple of times before and I love following his ramblings about JavaScript on the server side. I talked to him about why and how he came in contact with server side JavaScript in general and made him show a little more about his recent performance test, that he ran against RESTFUL backends (WIldFly and node.js). For (more...)

DBMS_INMEMORY_ADVISOR

When you follow the Oracle in-memory / optimizer team, then you have probably seen this…

Merge, Right?


"There are no wrong roads to anywhere."
 - Norton Juster, The Phantom Tollbooth 

Oracle can do some, well, strange things when fixing issues caused by the optimizer. For 10g releases up to 10.2.0.x Oracle chose to silently ignore a message and eliminate an outer join on the MERGE statement under certain conditions. Let’s examine this and see exactly what Oracle implements.

Occasionally in a 10046 trace file generated from 10g releases (more...)

ADF BC Range Paging and REST Pagination

In this post I would like to explore and integrate two thing - ADF BC Range Paging and REST service pagination. It would inefficient to retrieve entire set of data in the REST service, ideally should be available option to specify number of rows and range number to fetch. ADF BC allows to query VO in Range Paging mode - SQL query will be constructed with row numbers, to query data in certain range of (more...)

255 columns

Here’s a quick note, written and some strange time in (my) morning in Hpng Kong airport as I wait for my next flight – all spelling, grammar, and factual errors will be attributed to jet-lag or something.

And a happy new year to my Chinese readers.

You all know that having more than 255 columns in a table is a Bad Thing ™ – and surprisingly you don’t even have to get to 255 to (more...)

Latest updates to PerfSheet4, a tool for Oracle AWR data mining and visualization

Topic: This post is about the latest updates to PerfSheet4 v3.7 (February 2015). PerfSheet4 is a tool aimed at DBAs and Oracle performance analysts. It provides a simplified interface to extract and visualize AWR time series data using Excel pivot charts.


Why PerfSheet4: PerfSheet4 is aimed at querying and displaying time-series data from AWR repository tables. This is very a rich source of information to analyze database workloads and trends in the context of performance analysis or (more...)

Binary search – is it still most optimal?

If you have a sorted collection of elements, how would you find index of specific value?
"Binary search" is likely to be your answer.
Algorithms theory is teaching us what binary search is most optimal algorithm for this task with log(N) complexity.
Well, hash table can do better, if you need to find key by exact match. In many cases, though, you have reasons to have your collection sorted, not hashed.

On my job, I'm (more...)

MAF 2.1 Alta Mobile UI and Oracle Mobile Suite

This post is about Alta Mobile UI and MAF 2.1. I was using Oracle Work Better mobile application as a reference, along with Alta Mobile UI Design Guidelines. This is based on my previous posts about Oracle Mobile Suite and MAF 2.1 integration, read more here - Oracle Mobile Suite - Web Service Performance Optimisation with Result Caching. You could also use Alta UI 12c with regular ADF Web applications, check more here (more...)

To N or Not to N, is SYS_OP_C2C the Question; Oracle NVARCHAR Slow?

February 8, 2015 I was recently contacted about an odd performance issue with a software product named TDM, where certain SQL statements submitted to an Oracle 9.2.x database required roughly 30 seconds to execute when a nearly instantaneous response was expected.  The person who reported the issue to me provided a sample SQL statement that […]

Functions & Subqueries

I think the “mini-series” is a really nice blogging concept – it can pull together a number of short articles to offer a much better learning experience for the reader than they could get from the random collection of sound-bites that so often typifies an internet search; so here’s my recommendation for this week’s mini-series: a set of articles by Sayan Malakshinov a couple of years ago comparing the behaviour of Deterministic Functions and Scalar (more...)