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 22.214.171.124.0:
[oracle@dm01db01 [dbfs1] ~]$ dcli -g dbs_group -l oracle /u01/app/oracle/product/126.96.36.199/dbhome_1/bin/skgxpinfo dm01db01: rds (more...)
Although Oracle says that with Enterprise Manager 12c it “provides the tools to effectively and efficiently manage your Oracle Exadata Database Machine” it is a bit of a challenge to get it all working correctly on an Exadata V2. It looks like when developing the Exadata plugin for Enterprise manager 12c they clearly developed it on a X2 only, getting a V2 as a target into Enterprise Manager does not work out of the box. In order to get Enterprise Manager 12c to discover your Exadata V2 you need to do some extra steps.
Exadata discovery is done using the (more...)
As a DBA you are probably very curious on what is going on, on your system. So when you have a shiny Exadata you probably had a look at the infiniband fabric that is connecting the compute nodes and storage nodes together. When you want to see what kind traffic is going from the compute nodes to the storage nodes, or on the RAC interconnects you can use tcpdump to do so (if it is not install you can do a ‘yum install tcpdump’):
[root@dm01db02 ~]# tcpdump -i bond0 -s 0 -w /tmp/tcpdump.pcap tcpdump: WARNING: arptype 32 not supported (more...)
I have migrated several database to Exadata using Golden Gate and i really liked the Golden Gate tool. The only thing i never really understood is why there was not a simple Enterprise Manager plug-in to monitor the Golden Gate status. So i decided to create a small script that can be used as a ‘User Defined Metric’ in OEM. For monitoring purposes i am only interested in knowing if my process is abended (status stopped means that i have deliberately stopped it, so i don’t need to know that) and what the lag time is. So i have created (more...)