Written by From time to time, it happens to me to carry out offline analyses of ASH data. For that, I mean to analyze the ASH data without having access to the database instance that generated it. For that purpose, Oracle Database provides the possibility to dump the content of the ASH buffer as well as information […]
Read MoreScripts to Download Oracle Database 12c Release 2 Documentation
In the past (here, here and here) I already shared with you the scripts I use to download the Oracle Database documentation. The aim of this short post is to reference the scripts I just wrote for the latest version: 12c Release 2. download122.cmd download122.sh Happy downloading as well as happy reading!
Read MoreAdaptive Query Optimization: Backport of 12.2 Configuration in 12.1.0.2
I finally managed to install and test patch 22652097 (PROVIDE SEPARATE CONTROLS FOR ADAPTIVE PLANS AND ADAPTIVE STATISTICS FEATURES). Actually, I installed and tested two patches. The first was installed on top of “Oracle Database Patch 23054246 – Database Patch Set Update 12.1.0.2.160719” (from now on, 12.1.0.2.160719 PSU). The second was installed on top of […]
Read MoreAd – Oracle Database 12c Release 1 and 2: New Performance Features
In the past I gave a number of 1-day seminars about the new performance features available in Oracle Database 12c Release 1. On the 22nd of February, for the first time, I’ll give an updated version of that seminar with content about both Release 1 and Release 2. Note that because there is more content, […]
Read MoreInitialization Parameters Set at the PDB Level Are Not Always Honored
Before describing the issue that lead to this post, let’s shortly review how the handling of initialization parameters works in a multitenant environment. Initialization parameters exist at both the CDB level and the PDB level. This is a critical feature because it wouldn’t be acceptable to use the same set of initialization parameters for all […]
Read MoreApproximate Aggregate Transformation (AAT)
There are situations where approximate results are superior than exact results. Typically, this is the case when two conditions are met. First, when the time and/or resources needed to produce exact results are much higher than for approximate results. Second, when approximate results are good enough. Approximate results are for example superior in case of […]
Read MoreTrace Files Split in Multiple Parts
Last January, in the following tweet, I pointed out that the documentation vaguely mentions that a trace file may be split into several files. Did you successfully tested the new MAX_DUMP_FILE_SIZE behavior? If yes, which version/OS?https://t.co/4F9f9wsT95 pic.twitter.com/X2Y7FNf1HG — Christian Antognini (@ChrisAntognini) January 20, 2016 As a follow-up, few days later Jonathan Lewis published a post […]
Read MoreAdaptive Query Optimization Configuration: Parameters, Preferences and Fix Controls
The aim of this post is to summarize the knowledge about the 12.1 and 12.2 adaptive query optimizer configuration that, as far as I know, is spread over a number of (too many) different sources. First of all, let’s shortly review which adaptive query optimization features exist: Adaptive plans, which are only available in Enterprise […]
Read MoreSQL Trace in Oracle Database Exadata Express Cloud Service
Today I started having a look to the Oracle Database Exadata Express Cloud Service announced last week at Oracle OpenWorld. Note that since the amount of resources provided (in summary, 1 OCPU, 20 or 50 GB of database storage) is very limited, in general, in my opinion that service will only be useful for functional […]
Read MoreThe Broken Statistics: "parse count (total)" and "session cursor cache hits"
The values provided by the “parse count (total)” and “session cursor cache hits” statistics are subject to several bugs. And, what’s worse, for years Oracle didn’t care to fix it. This is my impression, at least. Then, when few weeks ago I read in the Oracle Support note 13837105.8 (Bug 13837105 – statistics “parse count […]
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