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An introduction to Policy Managed Databases in 11.2 RAC

I just realised this week that I haven’t really detailed anything about policy managed RAC databases. I remembered having done some research about server pools way back when came out. I promised to spend some time looking at the new type of database that comes with server pools: policy managed databases but somehow didn’t get around to doing it. Since I’m lazy I’ll refer to these databases as PMDs from now on as it saves a fair bit of typing.

So how are PMDs different from Administrator Managed Databases?

First of all you can have PMDs with RAC only, i.e. in a multi-instance active/active configuration. Before 11.2 RAC you had to tie an Oracle instance to a cluster node. This is why you see instance prefixes in a RAC spfile. Here is an example from my lab cluster:

Solaris Eye for the Linux Guy… Part III (hugepages = ISM)

This post has been a long time coming but recently, I have started working on some SPARC SuperCluster POC’s with customers and I am getting re-acquainted with my old friend Solaris and SPARC.

If you are a Linux performance guy you have likely heard of HugePages.   Huge pages are used to increase the performance of large memory machines but requiring fewer TLB‘s .  I am not going to go into the details TLB’s, but every modern chip supports multiple memory page sizes.

So how do you get huge pages with Solaris?

Do nothing – it is the DEFAULT with Oracle running on Solaris.

Linux large pages and non-uniform memory distribution

In my last post about large pages in I promised a little more background information on how large pages and NUMA are related.

Background and some history about processor architecture

More on use_large_pages in Linux and

Large Pages in Linux are a really interesting topic for me as I really like Linux and trying to understand how it works. Large pages can be very beneficial for systems with large SGAs and even more so for those with large SGA and lots of user sessions connected.

I have previously written about the benefits and usage of large pages in Linux here:

So now as you may know there is a change to the init.ora parameter “use_large_pages” in The parameter can take these values:

UltraEdit 4.0 for Mac/Linux…

UltraEdit 4.0 has been released for Mac and Linux. The downloads are in the usual place. You can see the latest changelogs here (Mac, Linux).

Fun, fun, fun…



When does an Oracle process know it’s on Exadata?

When an Oracle process starts executing a query and needs to do a full segment scan, it needs to make a decision if it’s going to use ‘blockmode’, which is the normal way of working on non-Exadata Oracle databases, where blocks are read from disk and processed by the Oracle foreground process, either “cached” (read from disk and put in the database buffercache) or “direct” (read from disk and put in the process’ PGA), or ‘offloaded mode’, where part of the execution is done by the cell server.

The code layer where the Oracle database process initiates the offloading is ‘kcfis’; an educated guess is Kernel Cache File Intelligent Storage. Does a “normal” alias non-Exadata database ever use the ‘kcfis’ layer? My first guess would be ‘no’, but we all know guessing takes you nowhere (right?). Let’s see if a “normal” database uses the ‘kcfis’ functions on a Linux x64 (OL 6.3) system with Oracle 64 bit using ASM.

Watching the “CopyBack” progress of a new disk on an Exadata compute node

This is just a very small post on how to watch the progress of the “CopyBack” state of a freshly inserted disk in an Exadata “Computing” (database) node. A disk failed in the (LSI Hardware) RAID5 set, and the hotspare disk was automatically used. The failed disk was replaced, and we are now awaiting the intermediate “CopyBack” phase.

The current state of the disks is visible using the following command:

Grid Infrastructure And Database High Availability Deep Dive Seminars 2013

So this is a little bit of a plug for myself and Enkitec but I’m running my Grid Infrastructure And Database High Availability Deep Dive Seminars again for Oracle University. This time these events are online, so no need to come to a classroom at all.

Here is the short description of the course:

Providing a highly available database architecture fit for today’s fast changing requirements can be a complex task. Many technologies are available to provide resilience, each with its own advantages and possible disadvantages. This seminar begins with an overview of available HA technologies (hard and soft partitioning of servers, cold failover clusters, RAC and RAC One Node) and complementary tools and techniques to provide recovery from site failure (Data Guard or storage replication).

Fedora 19 Alpha…

For those eager beavers out there, you can now get hold of Fedora 19 Alpha from the pre-release location.

The release notes can be found here. I’m keen to check out the improvements to MATE in version 1.6, as this is now my standard desktop.



Update: It installs in Oracle VirtualBox and the guest additions install correctly, so it’s looking good so far. :)

Exadata and the db_block_checksum parameter.

With Exadata version came the Unbreakable Linux Kernel for Exadata, which had been the stock EL5 redhat kernel prior to this version (2.6.18). With the unbreakable kernel came the opportunity to run the perf utility. This utility has the opportunity to see which functions are active inside an executable when there’s a symbol table. And the oracle database executable has a symbol table! One reason to do this, is to get a more granular overview of what the Oracle database is doing than the wait interface, especially to get a more detailed overview of what the database is doing in what is visible in the wait interface as ‘on cpu’.