Hello Readers … that is, if I still have any readers out left out there. I have few topics that have been on my mind lately and they will become posts in the near future. After all, this blog does have a purpose other than re-broadcasting my favorite xkcd's.First order of business is to let you know what I've been up to lately. As you may have already learned from other blogs and adverts,
Well it has been a while since my last blog. Things have been mad for the last months with delivering training, consulting and performing security audits, no time to stop and breath sometimes. I should not complain of course it....[Read More]
Posted by Pete On 02/12/10 At 05:48 PM
December 2, 2010 (Forward to the Next Post in the Series) It has been a couple of months since the last blog article that asked “What is Wrong with this Quote”, so I thought that I would try to add a couple of more blog articles to this series. I recently reviewed the book “Oracle Tuning [...]
Since the release of Oracle Database 11g I have made a few posts about Oracle NUMA awareness and the _enable NUMA_support parameter. There is an index of most of those posts here.
This is a really short blog entry about a little-known fact about the Oracle Database 11g Release 2 (22.214.171.124) default value for the _enable_NUMA_support initialization parameter in the Linux x86_64 port. The following is the if-then-else logic. There aren’t many initialization parameters (that I know of) that have so much logic around the default assignment.
At instance boot time, the booting foreground process performs “discovery” to see if there are Exadata Storage Servers available. If you strace instance startup you’ll see the following:
Also at boot time the numa libraries are dynamically linked and API calls are used to determine how many NUMA nodes there are. If there are more than 4 NUMA nodes and Exadata Storage is discovered the _enable_NUMA_support parameter is set to TRUE.
I have systems that attach to both Exadata and NFS storage at the same time. I have databases that reside entirely in both storage types as well. For maintenance reasons I needed to sever away the Exadata storage. That’s why the above discovery call suffered ENOENT. That changed my default setting for _enable_NUMA_support and in doing so my performance numbers changed dramatically because I was not explicitly setting _enable_NUMA_support = TRUE on the Sun x4800 system I was testing. The Sun x4800 is 8-socket Nehalem EX and 8-socket EX is something you don’t want to do without Oracle NUMA awareness. Well, at least not if the instance will be running on all processors.
I doubt any of you would ever run into this, but I thought it was worth a blog entry.
Filed under: oracle
December 1, 2010 Another recent blog article forced me to Stop, Think, … and just about understand (in case you are wondering about the blog title, the definition of invalid). Consider the following table definition: CREATE TABLE T3( V1 VARCHAR2(10), D2 DATE, N3 NUMBER); INSERT INTO T3 VALUES( CHR(65), TRUNC(SYSDATE)-65, [...]
It’s a week for polls !
Following a few comments on an old posting about the hash aggregation mechanism introduced by Oracle 10g (possibly 10.2) I’ve added a poll to my last comment to see how many people have had sufficient problems with it that they’ve decided to disable the feature. If you want to add your vote (and make a comment) go to: http://jonathanlewis.wordpress.com/2008/12/21/group-by/#comment-37975
I’ll be deleting this pointer in a few days, so I’ve disabled the comment and pingback features.
Update 2nd Dec: From a small starting sample (which isn’t necessarily a valid sample, of course) the poll is giving the impression that a significant number of people saw problems with this feature in 10g, but that the problems may have been eliminated by 11g.