Exadata and Virtual Private Database: will it offload my query?

During one of the classes I taught about Exadata optimisations I had an interesting question:

If I am using VPD, will Exadata still offload the query?

Background is that we discussed function offloading, and the meta-view v$sqlfn_metadata. It turned out that SYS_CONTEXT() is not offloadable in 11.2.0.4.

SQL> select name,datatype,analytic,aggregate,offloadable,descr
  2  from v$sqlfn_metadata where name = 'SYS_CONTEXT';

NAME                                               DATATYPE ANA AGG OFF DESCR
-------------------------------------------------- -------- --- --- --- ------------------------------
SYS_CONTEXT                                        UNKNOWN  NO   (more...)

Little things worth knowing-troubleshooting parallel statement queueing

This is yet another one of these posts that hopefully help you as much as they are going to help me in the future. Recently I enjoyed troubleshooting a problem related to parallel execution. Since I have never really written down how to tackle such a problem I thought it might be nice to do that now.

This is 12.1.0.2.0 on Exadata, but the platform doesn’t really matter for the troubleshooting (more...)

Interesting observation about standby redo logs in Data Guard

Some of you might have followed the discussion around the number of standby redo logs on twitter, but since 140 characters are woefully short for the complete story here’s the writeup that prompted the question. This is a test with 12.1.0.2 on virtualised Linux, repeated on a proper platform with physical hardware.

First of all here’s my setup. I have a dbca-based database (CDB, but doesn’t matter) that features 3 groups for (more...)

Can you have high redundancy files in a normal redundancy diskgroup?

One of the perks of teaching classes is that I get to research questions asked. In the last Exadata Administration Class I taught someone asked: can you have your disk groups in Exadata on normal redundancy yet have certain databases use high redundancy? This would be a good interview question …

The answer is yes, which I remembered from researching material on the 11g RAC book but I wanted to prove that it is the (more...)

Intra-Database IORM in action

I have been teaching the Enkitec Exadata Administration Class this week and made an interesting observation I thought was worth sharing with regards to IO Resource Management on Exadata.

I have created a Database Resource Manager (DBRM) Plan that specifically puts a resource consumer group to a disadvantage. Actually, quite severely so but the following shouldn’t be a realistic example in the first place: I wanted to prove a point. Hang-on I hear you say: you (more...)

A brief history of time^H^H Oracle session statistics

I didn’t intend to write another blog post yesterday evening at all, but found something that was worth sharing and got me excited… And when I started writing I intended it to be a short post, too.

If you have been digging around Oracle session performance counters a little you undoubtedly noticed how their number has increased with every release, and even with every patch set. Unfortunately I don’t have a 11.1 system (or (more...)

A first look at RAC 12c (part I)

I have recently upgraded my RAC 12.1.0.1.3 system to RAC 12.1.0.2 including the RDBMS installation. Currently I am updating my skills with information relevant to what I would normally have called 12c Release 2 (so that would also answer the question: when is 12c Release 2 coming out?). Then I realised I haven’t posted a first look at RAC 12c post yet-so here it comes.

There are (more...)

How to get insights into the Linux Kernel

This is probably as much a note-to-self as it can possibly be. Recently I have enjoyed some more in-depth research about how the Linux kernel works. To that extent I started fairly low-level. Theoretically speaking, you need to understand the hardware-software interface first before you can understand the upper levels. But in practice you get by with less knowledge. But if you are truly interested in how computers work you might want to consider reading (more...)

Upgrading clustered Grid Infrastructure to 12.1.0.2 from 12.1.0.1.3

Oracle 12.1.0.2 is out, after lots of announcements the product has finally been released. I had just extended my 12.1.0.1.3 cluster to 3 nodes and was about to apply the July PSU when I saw the news. So why not try and upgrade to the brand new thing?

What struck me at first was the list of new features … Oracle’s patching strategy has really changed over time. I (more...)

Implications of threaded_execution = true in 12c

I had an interesting discussion as part of my latest presentation at the UKOUG RAC CIA & Database Combined SIG. Part of my talk was about the implications of the new threaded execution model in Oracle.

Since “we do not use Windows” (except for gaming) I can’t compare the Windows thread model to the new 12c implementation on UNIX. There are however interesting implications when switching to the new model, some of which I’d like (more...)