Parallel Execution

This is another little reference list I should have created some time ago. It covers a series of posts on interpreting parallel execution plans and understanding where the work happens.

Poor mans getTracefile

As you might know already, I'm a big fan of Oracle Traces. Consequently I'm a fan of Method-R tools to work with these files as well.
A very important part in the chain of tools is Method R Trace - an extension to SQL Developer - as it speeds up developers a lot: When they generate a tracefile, they can access it immediately and do not need to ask and wait for a DBA to (more...)

How to Pass Arguments to OS Shell Script from Oracle Database

Imagine you have several Oracle databases on the same host under same OS user.

In scripts directory you have shell script that kills OS processes.
Idea is to call OS script from database procedure and kill problematic process using shell script.

Script will run simple query to get process id and kill that process.

But how to assure that this script will execute in correct environment for correct database?

One way is to create one (more...)

When a 12c upgrade unexpectedly breaks something – beware 9i!



The 12c upgrades continue to rumble on - this week we upgraded our cloud control repository (Oracle finally added support to be able to do this) - this all went fine however a couple of days later we had reports that the 'portal' isn't working.

Now the 'portal' is an ancient utility system developed in house that was considered to be unused (at least by us) - however it appeared that some user groups were (more...)

I’m a Millionaire now!

At least regarding the hits on this Blog :-) Thank you all for visiting uhesse.com!


ASM not starting with ORA-00845 – how to fix ASM parameter file

Few days ago I saw great post from Norman Dunbar on how to fix a broken ASM spfile.

With version 11gR2 ASM spfile can be stored in ASM diskgroup and by default Oracle Installer will put it there. So if you want to create pfile from spfile your ASM instance should be up and running.

If you have incorrect parameter in ASM spfile which is blocking ASM to start than you have slight problem. You (more...)

A Simple Introduction to ADDM and AWR

ADDM was introduced in Oracle 10 and stands for Automatic Database Diagnostic Monitor. You can use it to help solve performance problems. I was looking through some old copies of Oracle Magazine, found an article about it, written by Kimberly Floss in May/June 2004, and decided to give it a try. The article provided some SQL to produce an ADDM report so I ran it against an Oracle 12 database which nobody was using:

Log Buffer #422: A Carnival of the Vanities for DBAs

This Log Buffer Edition picks, choose and glean some of the top notch blog posts from Oracle, SQL Server and MySQL.

Oracle:

  • The standard images that come with devstack are very basic
  • Oracle is pleased to announce the release of Oracle VM VirtualBox 5.0 BETA 3
  • Monitoring Parallel Execution using Real-Time SQL Monitoring in Oracle Database 12c
  • Accessing your Cloud Integration API end point from Javascript
  • Are You Ready for The Future of Oracle (more...)

Cost

I’ve just been checking “Cost Based Oracle – Fundamentals” (Apress 2005) to see what I said on a particular topic, and I couldn’t resist quoting the following from the opening page of Chapter 1:

One of the commonest questions about the CBO on the Internet is: “What does the cost represent?” This is usually followed by comments like: “According to explain plan the cost of doing a hash join for this query is seven (more...)

Heuristic Temp Table Transformation – 2

Heuristic Temp Table Transformation - 2 Some time ago I've demonstrated the non-cost based decision for applying the temp table transformation when using CTEs (Common Table/Subquery Expressions). In this note I want to highlight another aspect of this behaviour.Consider the following data creating a table with delibrately wide columns:

create table a
as
select
rownum as id
, rownum as id2
, rpad('x', 4000) as large_vc1
, rpad('x', 4000) as large_vc2
, rpad('x', 4000) (more...)

SQL Performance, Part II — Disk I/O: metrics and scales

While query performance depends on a large number of things, overall scale of query performance for a given database is generally set by disk I/O speed. The most common type of a storage device used in databases is still a hard disk drive (HDD), so let’s consider how it works.

HDD uses magnetic state of a very small region on a disk to encode “0” or “1” (i.e. carry 1 bit of information). A (more...)

The Great Hypervisor Bake-off: VMware ESX vs Oracle VM

lock-horns

This is a very simple post to show the results of some recent testing that Tom and I ran using Oracle SLOB on Violin to determine the impact of using virtualization. But before we get to that, I am duty bound to write a paragraph of text featuring lots of long sentences peppered with industry buzz words. Forgive me, it’s just the way I’m wired.

It is increasingly common these days to find database environments running (more...)

Access Denied – Access to administration console is restricted

Access Denied - Access to administration console is restricted. Ran into it, today. Again. This time, I'll make a proper blog entry, not like this one... This time, I actually did follow my own advice, but for the fact, I now am working in a multi-homed WebLogic environment - I simply pasted the wrong WLS home...

Friday Philosophy – Know Your Audience

There are some things that are critical for businesses that can be hidden or of little concern to those of us doing a technical job. One of those is knowing who your customers are. It is vital to businesses to know who is buying their products or services. Knowing who is not and never will buy their products is also important (don’t target the uninterested) and knowing and who is not currently buying and might (more...)

edb360 taking a long time

In most cases edb360 takes less than 1hr to execute. But I often hear of cases where it takes a lot longer than that. In a corner case it was taking several days and it had to be killed.

So the question is WHY edb360 takes that long?

Well, edb360 executes thousands of SQL statements sequentially (intentionally). Many of these queries read data from AWR and in particular from ASH. So, lets say your ASH (more...)

Find Contents of RMAN backuppiece

RMAN backuppiece listings from OS

oracle@arrow:hawklas:/home/oracle
$ ll /oradata/backup/
total 216088
-rw-r-----. 1 oracle oinstall  1212416 May  5 11:06 DBF_HAWK_3130551611_20150505_hjq65thu_1_1_KEEP
-rw-r-----. 1 oracle oinstall 50536448 May  5 11:07 DBF_HAWK_3130551611_20150505_hkq65thu_1_1_KEEP
-rw-r-----. 1 oracle oinstall 39059456 May  5 11:07 DBF_HAWK_3130551611_20150505_hlq65thv_1_1_KEEP
-rw-r-----. 1 oracle oinstall  5529600 May  5 11:07 DBF_HAWK_3130551611_20150505_hmq65tie_1_1_KEEP
-rw-r-----. 1 oracle oinstall  1785856 May  5 11:07 DBF_HAWK_3130551611_20150505_hnq65tit_1_1_KEEP
-rw-r-----. 1 oracle oinstall    98304 May  5 11:07 DBF_HAWK_3130551611_20150505_hoq65tjd_1_1_KEEP
-rw-r-----. 1 oracle oinstall     2560 May  5 11:07 DBF_HAWK_3130551611_20150505_hpq65tjf_1_1_KEEP
-rw-r-----.  (more...)

SQL Performance, Part I. Data access efficiency.

Database performance optimization deals with the problem of reducing time (and/or other resources) required to complete database queries by resolving various inefficiencies. There are many kinds of performance issues, and they can be categorized in many different ways. One important way is by scope: statement-level or instance-level. Instance-level performance tuning (which we are not covering in this mini-series) deals with such problems as excessive parsing, cache efficiency, concurrency etc. Statement-level performance tuning deals mostly with (more...)

Giving back

Occasionally, I receive requests to explain stuff I talk about in my blog posts on a level accessible to beginners. Unfortunately, it’s not always possible to do so. You start to explain one little thing, and then you realize that in order to understand that thing, one would to understand a dozen other little things, and before you know it, instead of writing a short blog post you find yourself writing something of the size of (more...)

Finding the Oracle Database Appliance Plug-in within #em12c

The Oracle Database Appliance (ODA) has been around for a few years now. It is a great, compact, and powerful machine for running at two-node Oracle Real Application Cluster (RAC). The adoption of the ODA has been mostly seen in medium sized organizations that need a work horse but cannot afford the sticker price of an Oracle Exadata.

Just like all the appliances that Oracle puts out, there is a need to monitor these appliances (more...)

Apache Cassandra – NoSQL storage solution

These days I am exploring another storage solution – Cassandra.

Apache Cassandra datastore was originally developed by Facebook as open source NoSQL data storage system. Its actually based on Amazon’s dynamoDB database. Apache Cassandra is an open source distributed database management system designed to handle large amounts of data across many commodity servers, providing high availability with no single point of failure. Cassandra offers robust support for clusters spanning multiple datacenters, with asynchronous masterless replication allowing low latency operations (more...)