Recently we noticed that imageinfo was displaying the following information at a customers site. Imageinfo was not displaying data i suspected, so a quick little blogpost about what was going on there.
[root@dm01db01 ~]# dcli -g /opt/oracle.SupportTools/onecommand/dbs_group -l root "imageinfo | grep 'Image version'"
dm01db01: Image version: 11.2. (more...)
With cellcli you can run the calibrate command, this will measure the performance of your harddisks and flashcards. It will eventually report to you the throughput and amount of IOPS that was measured during the calibrate, it will also report to you which luns are not performing up to par.
Last year Oracle added a new functionality to dbms_stats.gather_system_stats, making it more Exadata aware and thus let the optimizer make choices that might result in offloading more often. See this blog post from Kerry Osborne about it, i made a small comment about the MBRC in it and i (more...)
I have seen several clients who are struggling to decode page allocation failures on Exadata, in this post i will try to explain how to read the backtrace. The following is an anonymized client case where page allocation failures are leading up to a node reboot.
Jan 1 11:58:02 dm01db01 (more...)
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 (more...)
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:
Interestingly enough it states that Oracle considers installation with +1000 targets as a medium sized em12c environment. That limit of +1000 targets is reached (more...)
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:
[root@dm01db01 ~]# tcpdump -i bondeth0 -s 0 port 53
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on bondeth0, link-type EN10MB (Ethernet), capture size 65535 bytes
15:41:04.937009 IP dm0101.domain.local.59868 > dnsserver01. (more...)
Hybrid Columnar Compression (HCC) is one of the Exadata features but lately Oracle has been pushing this featurei to other Oracle hardware like the ZFS Storage Appliance and Axiom Pillar Storage series. We recently got a ZFS Storage Appliance (ZFSSA) at VX Company, so we are now able to use HCC on the Oracle Database Appliance (ODA). To use HCC we need to create a tablespace with datafiles on a ZFS Storage Appliance, in order to de so we going to hookup our ODA using directNFS (dNFS). I am not going in the details of explaining dnfs in this blogpost, (more...)
Recently i was asked to assist an ongoing issue at a customers site were one query was giving a a lot of problems. After a short investigation it turned out the application was using USE_NL hint in this select statement, which worked fine on a small table but crippled performance as the table grew. Now for several reasons the application code could not be changed within reasonable timeframe, so i created a SQL profile for this statement, which ignored all optimizer hints used in the statement.
Lets execute a query with an index hint as an example (using pipo_de_clown as (more...)
Recently i got a question from an Exadata customer what would happen if you would forget to relink the oracle for IPC RDS use for just one home. Would Oracle be smart enough to fall back on UPC for the complete RAC database? Time to do a little test and find out what will happen here:
First lets see how IPC communication between the nodes is done right now. We can use skgxpinfo to see how it is linked since version 220.127.116.11.0:
[oracle@dm01db01 [dbfs1] ~]$ dcli -g dbs_group -l oracle /u01/app/oracle/product/18.104.22.168/dbhome_1/bin/skgxpinfo