Johnathan Lewis (@JLOracle) recently published a short post about Stats Collection Time, talking about the table dba_optstat_operation (and dba_optstat_operation_tasks ), which reminded me about (what I regard as) an anomaly in the output in the NOTES columns in Oracle 12C.
I won’t repeat why it’s useful to check these tables as Johnathans note and @MDWidlakes’s comment here should give you all you need to know.
The DBA_OPTSTAT_OPERATION.NOTES column contains the (more...)
Yesterday I posted a note about querying dba_optstat_operations to get a quick report of how long calls to dbms_stats had been taking but said I had another script that helped to fill some of the gaps it left. One of my readers points out fairly promptely that 12c enhances the feature considerably, with a view dba_optstat_operation_tasks that (for example) lists all the tables processed during a single call to gather_schema_stats.
Well, I wrote my script (more...)
This post is about performance optimizations introduced in Apache Spark 2.0, in particular whole-stage code generation. A test case is introduced and investigated with diagnostic tools.Introduction: performance troubleshooting of a slow query using parallel query execution in a Hadoop cluster
The idea for this post comes from a performance
troubleshooting case that has come up recently on our database services. It started with a user reporting slow response time from a query (more...)
I don’t really remember how long it’s been since Oracle created an automatic log of how long a call to the dbms_stats package took, though it was probably some time in the 10g time-line. It wasn’t until it had been around for several years, though before I wrote little script (possibly prompted by a comment from Martin Widlake) that I’ve used occasionally since to see what’s been going on in the past, how variable (more...)
Is that enough version numbers for you?
The issue this post will address (very briefly because it’s the week before OOW2016 and life is crazy!) is this. If you are running a 13.1 version of the OMS, and you try to push a 188.8.131.52 agent to a Linux box that’s running some version of 5.x (such as RHEL5 or OL5), you will get an error message saying you are (more...)
How to install Oracle EM 13c? It's the first time that I have a chance to install Oracle EM 13c. I remember last time I installed Oracle EM 12c. I have to install weblogic first. On OEM 13c, I don't need to do something like that. It installs WLS -184.108.40.206 , JDK – 1.7.0_80.
In this post, I installed Oracle EM 13c Silent mode with "SMALL" deployment. I assume, I installed (more...)
So this customer has an Exadata quarter rack and they have an IB listener configured on both DB nodes (for DB connections from a multi-racked Exalogic system). We were adding a new DB node to this rack. So just followed the standard procedure of creating users, directories etc on the new node, setting up ssh equivalence and running addNode.sh. All went fine but root.sh failed. Little looking into the logs revealed that it (more...)
A script hacked together a couple of years ago from a clone of a script I’d been using for checking space usage in the older types of segments. Oracle Corp. eventually put together a routine to peer inside securefile LOBs:
rem Script: dbms_space_use_sf.sql
rem Author: Jonathan Lewis
rem Dated: Dec 2013
rem Last tested
rem Not tested
rem 11.1. (more...)
Op maandag 24 oktober vindt er een bijeenkomst plaats over JSON en de In-Memory Database…
This is just a short note that links to different articles on Alberto Dell'Era's blog. Alberto is a long time member of the OakTable and has published a number of posts I find very useful and therefore are linked here:ASH wait times (including an ASH simulator!)Posts on Materialized Views
One of the nice things about declaring your (basicfile) LOBs as “enable storage in row” is that the block addresses of the first 12 chunks will be listed in the row and won’t use the LOB index, so if your LOBs are larger than 3960 bytes but otherwise rather small the LOB index will hold only the timestamp entries for deleted LOBs. This makes it just a little easier to pick out the information you (more...)
At the end of the last installment we had seen a test case that caused Oracle to add a couple of redundant new extents to a LOB segment after one process deleted 3,000 LOBs and another four concurrent processes inserted 750 LOBs each a few minutes later (after the undo retention period had elapsed). To add confusion the LOBINDEX seemed to show that all the “reusable” chunks had been removed from the index which suggests (more...)
Here’s a simple script that I’ve used for many years to check space usage inside segments. The comment about freelist groups may be out of date – I’ve not had to worry about that for a very long time. There is a separate script for securefile lobs.
rem Script: dbms_space_use.sql
rem Author: Jonathan Lewis
rem Dated: Nov 2002
rem Last tested
rem 11.2. (more...)