Posted by Riyaj Shamsudeen on September 28, 2011
I will be talking about “Administering Parallel Execution in RAC” with demos on Sunday morning 9AM-10AM (session id 28060). This is part of IOUG RAC SIG presentation series. You would enjoy the content and demos I have prepared.
I know, it is too early, but hoping to see you there!
BTW, if you have attended my RAC Advanced Troubleshooting class series, please don’t hesitate to introduce yourself when we meet.
Session ID: 28060
Session Title: IOUG: Administering Parallel Execution in Oracle RAC
Venue / Room: Moscone West- 2005
Date and Time: 10/2/11, 9:00 – 10:00
Update: I just completed this session in IOUG. Thank you for coming, if you were in the room.
You can download the pdf file from
PX execution in RAC
Posted in 11g, Performance tuning, Presentations, RAC | Tagged: 11g, oracle performance, parallel_instance_group, RAC, RAC performance | 4 Comments »
Posted by Riyaj Shamsudeen on June 20, 2009
I presented about various performance myths in my ‘battle of the nodes’ presentation. One of the myth was that how spawning parallel query slaves across multiple RAC instances can cause major bottleneck in the interconnect. In fact, that myth was direct result of a lessons learnt presentation from a client engagement. Client was suffering from performance issues with enormous global cache waits running in to 30+ms average response time for global cache CR traffic and crippling application performance. Essentially, their data warehouse queries were performing hundreds of parallel queries concurrently with slaves spawning across three node RAC instances.
Of course, I had to hide the client details and simplified using a test case to explain the myth. Looks like either a)my test case is bad or b) some sort of bug I encountered in 126.96.36.199 version c) I made a mistake in my analysis somewhere. Most likely it is the last one😦. Greg Rahn questioned that example and this topic deserves more research to understand this little bit further. At this point, I don’t have 188.8.131.52 and database is in 10.2.0.4 and so we will test this in 10.2.0.4.
UDP is one of the protocol used for cache fusion traffic in RAC and it is the Oracle recommended protocol. In this article, UDP traffic size must be measured. Measuring Global cache traffic using AWR reports was not precise. So, I decided to use a dtrace tool kit tool:udpsnoop.d to measure the traffic between RAC nodes. There are two RAC nodes in this setup. You can read more about udpsnoop.d. That tool udpsnoop.d can be downloaded from dtrace toolkit . Output of this script is of the form:
PID LADDR LPORT DR RADDR RPORT SIZE
---------- --------------- --------------- ---------- --------------- --------------- -----------
15393 184.108.40.206 38395 -> 220.127.116.11 40449 8240
Posted in Oracle database internals, Performance tuning, RAC | Tagged: battle of the nodes, external table, gv$px_session, oracle, oracle performance, parallel query, parallel_instance_group, RAC interconnect traffic, RAC performance myths, UDP, udpsnoop.d | 15 Comments »