This is the third part of the video tutorial "Analysing Parallel Execution Skew". In this part I show how to analyse a parallel SQL execution regarding Parallel Execution Skew.
If you don't have a Diagnostics / Tuning Pack license the options you have for doing that are quite limited, and the approach, as demonstrated in the tutorial, has several limitations and shortcomings.
Here is the video:
If you want to reproduce or play around with (more...)
A minor update 4.01 to the XPLAN_ASH utility is available for download.As usual the latest version can be downloaded here.
These are the notes from the change log:
- More info for RAC Cross Instance Parallel Execution: Many sections now show a GLOBAL aggregate info in addition to instance-specific data
- The Parallel Execution Server Set detection and ASSUMED_DEGREE info now makes use of the undocumented PX_STEP_ID and PX_STEPS_ARG info (bit mask part (more...)
Readers of an earlier post on this blog
will know about my latest forays into the world of Direct NFS. Part of that means stumbling over configuration hiccups or slamming into brick walls when you find new bugs.
To quickly re-set the table, my organization purchased the Oracle ZFS Storage Appliance (ZFSSA) 7420
. Oracle sold us on the Infiniband connectivity as a way to make a possible future transition to Exadata easier. However the pre-sales (more...)
In this post, I’m installing the Oracle Database 11g Release 2 (126.96.36.199) software on Oracle Linux 6.4, along with optional instructions on how to apply the latest Patch Set Update (PSU) to your new Oracle home. First and foremost, before you start, make sure your Linux server meets the minimum hardware requirements: 1GB of RAM (plus
A new version of the XPLAN_ASH tool (detailed analysis of a single SQL statement execution) is available for download. The previous post
includes links to video tutorials explaining what the tool is about.As usual the latest version can be downloaded here.
The new version comes with numerous improvements and (more...)
I just uploaded my DOAG 2013 presentation “Best of Oracle Security 2013“.
This presentation shows how to bypass Oracle Data Redaction, become DBA using CREATE ANY INDEX, Hide information from Oracle Auding using VPD and more…
SQL> select * from scott.credit_card where 1=ordsys.ord_dicom.getmappingxpath((card_id),user,user);
When the optimizer has to estimate the data volume (the BYTES
column in the plan output), it usually bases this information on the column statistics
, if applicable and available (think of complex expressions).However, whenever there is a VIEW operator
in an execution plan, that represents an unmerged view, the optimizer obviously "loses" this information and starts applying defaults that are based on the column definition
.Depending on the actual content of the columns (more...)
Yesterday I was creating a new Oracle 188.8.131.52 database from a copy of datafiles and archivelogs taken from our standby. I was sure to include archivelogs from just prior to well after the span of the datafile backup time. I had created a new controlfile, gotten everything (more...)
At Derbycon 3.0, László Tóth and Ferenc Spala gave a a new presentation “What’s common in Oracle and Samsung? They tried to think differently… ” (Video). The main focus of the presentation was the Samsung encryption and a new framework called sandy but there was also a small (more...)
2 days ago I gave a presentation “Oracle 12c from the attackers perspective” at the DOAG SIG Security. I learned some interesting things, especially that a fix for the Oracle oradebug “disable auditing” problem is available since 9 months.
Oradebug allows to run OS commands and to enable/disable Oracle SYSDBA (more...)
Enterprise Manager Oracle Management Server (OMS) installations generate huge amounts of log and trace files under the covers these days, and although the logs are rotated out-of-the-box, they’re not automatically deleted. Over time (as I was reminded again today ), these logs can amount to a large portion of your (more...)
The TIMESTAMP WITH TIME ZONE data type that got introduced a long time ago is known for some oddities, for example Tony Hasler has a nice summary of some of them here
.Here is another oddity that shows up when trying to aggregate on such a data type. Have a look at the following simple example:
create table t
rownum as id
, date '2000-01-01' + rownum - 1 as some_date
, cast(date (more...)
Original Post can be viewed at portmap: unrecognized service on RHEL6
Quick note for people using NFS for shared storage on RAC database. Till RHEL5 we had to ensure nfs,nfslock and portmap service has to be running. These services are required otherwise you will get following errors while mounting database (more...)
A new major release (version 3.0) of my XPLAN_ASH tool is available for download.You can download the latest version here.
In addition to many changes to the way the information is presented and many other smaller changes to functionality there is one major new feature: XPLAN_ASH now also supports S-ASH
, the free ASH implementation.
If you run XPLAN_ASH in a S-ASH repository owner schema, it will automatically detect that and adjust accordingly. (more...)