Posts tagged Oracle
Direct path read and fast full index scans
May 9th
This is yet another blogpost on Oracle’s direct path read feature which was introduced for non-parallel query processes in Oracle version 11.
Exadata V2 and CPU scaling
May 5th
A while ago I was doing some bandwith and latency testing of infiniband interfaces on different Exadata configurations and ran into something that might be interesting for Exadata V2 owners out there. You can do some performance test on your IB stack using a set of tools that start with ib_read_*, ib_send_* and ib_write_*. These tools work in a client/server setting where you start a server on side of your path and start a client on the side and start sending and reading data. When running these tests on an Exadata X2 and higher your output will look somewhat like this:
When does an Oracle process know it’s on Exadata?
May 4th
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.
Watching the “CopyBack” progress of a new disk on an Exadata compute node
May 3rd
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.
Exadata and the db_block_checksum parameter.
Apr 6th
With Exadata version 11.2.3.2.0 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’.
RMOUG and Hotsos
Apr 5th
Recently I’ve spoken at the RMOUG training days 2013 in Denver (the mile high city). It was a first time for me to speak for the RMOUG and being in Denver. Thanks to the “sequestration” (federal budget cuts) the lines piled at immigration at Minneapolis (Minneapolis and Saint Paul, the twin cities) airport, and because my plane left more than one hour to late and my layover time was one hour and fifteen minutes, I tried to rebook my flight from Minneapolis to Denver. But, this flight turned out to be delayed too. This meant I was able to get on this flight!
Observing how Oracle Exadata SmartScans internals work, part 1
Mar 31st
In order to look how Exadata smartscans are different, first let’s have a peek the Oracle full segment/multiblock read evolution as short as possible:
Observing Oracle Exadata SmartScan internals, part 1
Mar 31st
In order to look how Exadata smartscans are different, first let’s have a peek the Oracle full segment/multiblock read evolution as short as possible:
Changing the heap size of Enterprise Manager 12c
Mar 14th
Enterprise Manager 12c is a product that is being deployed a lot lately, a vast improvement over previews version. For most DBA’s it is a tool they use regularly on a daily basis so performance is key. Fortunately oracle provides us with some documentation on how to size the repository database and heap size of the Oracle Management Service. An excellent white paper on EM12c sizing can be found here on OTN:
Exadata versus IPv6
Feb 3rd
Recently one of my customers got a complaint from their DNS administrators, our Exadata’s are doing 40.000 DNS requests per minute. We like our DNS admins so we had a look into these request and what was causing them. I started with just firing up a tcpdump on one of the bonded client interfaces on a random compute node:
