Prompted by an actual task at hand I spent some time investigating an 184.108.40.206 feature – concurrent statistics gathering. It has been on my to-do list for quite some time but so far I didn’t have a use case, and use cases make it so much easier. The question was-how can I gather statistics on a really large, partitioned table? Previously, you could revert to the degree in dbms_stats.gather_table_stats to ensure that (more...)
If you ever wanted to know how Clusterware works with registered database resources, read on! It takes a little while to get your head around the concepts of the ORACLE_SID, the instance_name and the database name as well. And how Clusterware deals with all of them. Although this post has been written on 220.127.116.11.0 on Linux, it should be applicable to 11.2 Clusterware as well. Oh and by Clusterware I (more...)
My lab server has 2 SSDs, one is connected using SATA 2 and another is connected using SATA 3. I’d expect the SATA 3 connected device to be equally well equipped or even better to do work than the “old” interface. I ran SLOB on these devices to find out if there was a difference. To my great surprise the SATA2 – connected SSD performed a lot better than the SATA 3 device, as shown (more...)
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$sqlfn_metadata. It turned out that SYS_CONTEXT() is not offloadable in 18.104.22.168.
SQL> select name,datatype,analytic,aggregate,offloadable,descr 2 from v$sqlfn_metadata where name = 'SYS_CONTEXT'; NAME DATATYPE ANA AGG OFF DESCR -------------------------------------------------- -------- --- --- --- ------------------------------ SYS_CONTEXT UNKNOWN NO (more...)
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 22.214.171.124.0 on Exadata, but the platform doesn’t really matter for the troubleshooting (more...)
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 126.96.36.199 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...)
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...)
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...)
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...)
I have recently upgraded my RAC 188.8.131.52.3 system to RAC 184.108.40.206 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...)