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...)

Setting up Direct NFS on Oracle 12c

Direct NFS is a great feature that I have finally had the time to investigate further. Since I always forget how to set it up and I didn’t find blog posts about this subject elsewhere I decided to put something together.

In this configuration I am using a virtual machine named server1 to export a directory to server2. Oracle is not as lenient as myself and may have certain support requirements when it comes to (more...)

Why is P1 the only parameter populated in cell smart table scan?

Anyone who has looked at Exadata might ask the question, and I did so too. After all, cell smart table scan is in wait class User IO so there should be more, right? This is what you find for a smart scan:

NAME                           PARAMETER1           PARAMETER2           PARAMETER3                     WAIT_CLASS
------------------------------ -------------------- -------------------- ------------------------------ ---------------
cell smart table scan          cellhash#                                                                User I/O
cell smart index scan          cellhash#                                                                User I/O

Compare this to the traditional IO request:

NAME                           PARAMETER1           PARAMETER2            (more...)

Why does the Optimiser not respect my qb_name() hint?

I recently was involved in an investigation on a slow-running report on an Exadata system. This was rather interesting, the raw text file with the query was 33kb in size, and SQL Developer formatted the query to > 1000 lines. There were lots of interesting constructs in the query and the optimiser did its best to make sense of the inline views and various joins.

This almost lead to a different post about the importance (more...)

My SDU goes to 11 ^h^h I meant 2097152

One of the cool new things in 12.1 is that you can set the Session Data Unit to 2MB. This might not sound like a Big Deal, but getting this to work required me to dig deeper into the TNS layer than I intended…Then I somehow got stuck on the wrong track, thankfully the team at Enkitec helped out here with pointers.

This post is rather boring if you just look at it but (more...)

RAC 12c enhancements: adding an additional SCAN-part 4

This is going to be the last part of this series, however long it might end up being in the end. In the previous articles you read how to create a physical standby database from a RAC One database.

Networks (refresher)

To make it easier to follow without going back to the previous articles, here are the networks I’m using, listed for your convenience.

  • 192.168.100/24: Client network
  • 192.168.102/24: Dedicated Data Guard (more...)

Mysterious new Oracle compression type

As part of our research for our joint presentation at and E4 my colleague Frits Hoogland made an interesting discovery. He verified the compression format for updated rows previously compressed using Hybrid Columnar Compression (HCC). In that particular example we researched HCC data on Exadata storage. As you may know, reading HCC data in its compressed form is limited to Exadata, Pillar Axiom, and the ZFS Storage Appliance (ZFSSA).


So far I (more...)

RAC 12c enhancements: adding an additional SCAN-part 3

Travel time can be writing time and while sitting in the departure lounge waiting for my flight I use the opportunity to add part 3 of the series. In the previous two parts you could read how to add a second SCAN and the necessary infrastructure to the cluster. Now it is time to create the standby database. It is assumed that a RAC One Node database has already been created on the primary cluster (more...)

RAC 12c enhancements: adding an additional SCAN-part 2

In the first part of this article you could read how to add an additional network resource, additional VIPs and SCAN to an cluster. In this part I hope to show you the next steps such as adding the SCAN listeners and other resources.

New SCAN listener

With the second SCAN added it is time to add the next set of SCAN listeners. This is really simple, and here is (more...)

RAC 12c enhancements: adding an additional SCAN-part 1

Based on customer request Oracle has added the functionality to add a second SCAN, completely independent of the SCAN defined/created during the cluster creation. Why would you want to use this feature? A few reasons that spring to mind are:

  • Consolidation: customers insist on using a different network
  • Separate network for Data Guard traffic

To demonstrate the concept I am going to show you in this blog post how I

  1. Add a new network resource
  2. (more...)