Script: Inactive Parallel QC Holding Parallel Processes

Working on a data warehouse system can be quite challenging, as I mentioned in the post from yesterday. One of the things we need to take care of is the amount of parallel processes that are in used at all times. Yesterday I wrote about how to locate downgraded sessions. Today we will look at another aspect – who “steals” parallel processes and what can we do to solve it.

One of the biggest thieves (more...)

Troubleshooting EBS 12.2 JDBC Connection Leaks

Within Oracle WebLogic Server 10.3.6, Oracle E-Business Suite Release 12.2 employs Java Database Connectivity (JDBC) data sources to maintain a pool of connections for database connectivity. These JDBC data sources are associated with the managed servers (such as oacore and forms) in which Oracle E-Business Suite applications are deployed.

Connections are checked out and then returned to the data source when the request is complete. A connection is said to be leaked (more...)

Script: Finding Session With Downgraded Parallel Execution

I was working with the data warehouse team at a customer site and at some point we realized that some parallel executions are not getting enough resources (downgraded).

Not getting enough parallel processes in such a complex environment is really bad. That means that since everybody is hogging the CPU, some sessions will not be able to complete inside the night ETL time frame. If that happens – some ETLs will go on into the (more...)

Oracle Database Cloud (DBaaS) Performance – Part 2 – Storage

In this second part of this installment I'll focus on the performance figures related to I/O encountered when the corresponding tests were performed on the platform.


When running with minimum sized buffer cache, direct and asynchronous I/O enabled, the following average read-only IOPS figures were measured over a period of several days (this is the test described in part three of the "performance consistency" series) .

First, running on a 4 OCPU single instance configuration (more...)

web scale patterns in the back office – Event Sourcing

web scale patterns in the back office – Event Sourcing

Last week we started a series of blog posts we show you how we use “web scale” patterns to achieve scaleability and flexibility in our back office software. Last weeks pattern we discussed was CQRS. This week we will dive in to Event Sourcing. Showing you how this doesn’t just solve a technical problem, they helps us solve our business problems!

Event Sourcing


Manually Generating AWR Report

One of my customers asked me to check performance on his production database server but could not allow any access to the server itself. He asked if I could generate the AWR reports from his client machine and since it’s not really trivial (or hard) I created this script.

When we want to generate the AWR report, we usually run the awrrpt.sql script. We don’t need to be on the database server for that (more...)

Script: Finding the Top N Queries for a User (AWR)

In some conditions, I need to find the top N queries for a specific user in the database.
Assuming my customer is running Enterprise Edition and have tuning pack licenses, it is easy enough to pull the data off the Automatic Workload Repository (AWR).

For some reason, a lot of DBAs are not aware that the AWR report is just a report – and you can query the base table yourself to extract more information (more...)

Oracle Database Cloud (DBaaS) Performance – Part 1 – CPU

After having looked at the performance consistency provided by the Oracle Database Cloud offering in the previous series, I'll focus here on the raw performance figures I've measured during my tests, starting with the CPU related performance findings.

One of the first surprises is related to the fact that Oracle uses a unit called "OCPU" to specify the CPU capacity provided, which is explained here:

So one "OCPU" is supposed to represent one core (more...)

Skip LOV Validation for ADF BC Bulk Insert

This post is about ADF BC LOV. I will describe how you could optimize bulk insert of new rows into VO, when some of the attributes are assigned with LOVs. By default ADF would validate new row attribute value through LOV (LOV Validation and Programmatic Row Insert Performance) for each new row. This will lead to bad performance, especially if you insert a set of new rows programmatically - there will be multiple (more...)

eProseed Oracle Open World 2016 debrief – Oracle Database & Oracle Management Cloud

For people interested, here the slide desks used internally to debrief my colleagues regarding Oracle…

Scanning an Index

The internet is full of information about indexes, and for a reason. Indexes in a database is probably the most important performance related topic. There are so many cases, properties, and different ways to use indexes that there is simply a lot to write about. In this post I’d like to talk about a specific … Continue reading Scanning an Index

WebLogic Server: Automate obtaining performance metrics from the DMS

Oracle provides the Dynamic Monitoring Service (DMS) as part of WebLogic Server which is extremely useful if you want to obtain aggregated data of an environment in case of for example a performance test. The data which can be obtained from DMS is extensive. This varies from average duration of service calls to JVM garbage collects to datasource statistics. DMS can be queried with WLST. See for example here. On example script based on this (more...)

Investigating IO Performance on Amazon RDS for Oracle

I’ve recently been involved in quite a few database migrations to Oracle RDS. One thing that I had noticed when dealing with post-migration performance issues was related to queries that used TABLE SCAN FULL in their execution. It seemed, that in many cases, it just took a single query to max out the allocated IOPS (IOs per second) or bandwidth, which in turn would caused overall slowness of the RDS instance.

The search in documentation (more...)

Why oh Why Do Will Still Not Have a Fast Bulk “SQL*Unloader” Facility?

Way back in 2004 I was working at the UK side of the Human Genome project. We were creating a massive store of DNA sequences in an Oracle database (this was one of two world-wide available stores of this information, for free & open use by anyone {* see note!}). The database was, for back then, enormous at 5-6TB. And we knew it would approx double every 12 months (and it did, it was (more...)

Do you suffer from Storage Stockholm Syndrome?

The last year at DSSD (now a part of Dell EMC) has been an extremely interesting one for me, and I’ve learned a great deal, which is always good. Some of the lessons have been surprising, though… One of them is what I will rather dramatically refer to as Storage Stockholm Syndrome. Stockholm Syndrome is … Continue reading "Do you suffer from Storage Stockholm Syndrome?"


Many of the questions that appear on OTN are deceptively simple until you start thinking carefully about the implications; one such showed up a little while ago:

What i want to do is to delete rows from table where it matches condition upper(CATEGORY_DESCRIPTION) like ‘%BOOK%’.

At the same time i want these rows to be inserted into other table.

The first problem is this: how carefully does the requirement need to be stated before (more...)

cost vs. gets

Last week I hit an interesting performance issue:
A Table (T) has 2 index (of interest). One (IX_1) is only on column S, the other (IX_2) on (C, S).
The optimizer calculates the plan with IX_1 more expensive than the plan with IX_2 - as this should be more selective.
But the gets for the plan with IX_1 were less than those the optimizer preferred.

Here the information about the statement, index and plans.
As (more...)

Friday Philosophy – Your Experience can Keep You Ignorant

This week I was in an excellent presentation by Kerry Osborne about Outlines, SQL profiles, SQL patches and SQL Baselines. I’ve used three of those features in anger but when I looked at SQL Patches I just could not understand why you would use them – they looked to me like a very limited version of SQL Profiles.

There is a prize for spotting Kerry without a baseball cap

There is a prize for spotting Kerry without a baseball cap

So I asked Kerry about it (more...)

#DOAG2016 wrap up


Another DOAG is over and here are my summary.

Day 1

Unfortunately the early train from duesseldorf arrives not before 9:30, so I missed the first morning slot. But on the other hand I this was the slot where I had to decide between 8 presentations, which I’m interested in.

The first soft skill presentation was about creative techniques beyond brain storming. The mentioned 3 techniques was all unknown for me, maybe I give it (more...)

“If You Change This, Right Here …”

"changes are so frightening."
-- Norton Juster, The Phantom Tollbooth

It isn’t unusual for Oracle to expand functionality with each new release; a short list includes AWR, ADDM, the SYSAUX tablespace, Flashback Query, Flashback Database and Edition-based Redefinition. Oracle 12.1 is no different as it provides an interesting performance enhancement, the in-memory column store, that can increase performance by reducing physical I/O load by making tables memory-resident (to simplify the description somewhat). Inn (more...)