I just realised this week that I haven’t really detailed anything about policy managed RAC databases. I remembered having done some research about server pools way back when 188.8.131.52 came out. I promised to spend some time looking at the new type of database that comes with server pools: policy managed databases but somehow didn’t get around to doing it. Since I’m lazy I’ll refer to these databases as PMDs from now on as it saves a fair bit of typing.
So how are PMDs different from Administrator Managed Databases?
First of all you can have PMDs with RAC only, i.e. in a multi-instance active/active configuration. Before 11.2 RAC you had to tie an Oracle instance to a cluster node. This is why you see instance prefixes in a RAC spfile. Here is an example from my lab 184.108.40.206.6 cluster:
This blog entry is to discuss a method to identify the objects inducing higher amount of redo. First,we will establish that redo size increased sharply and then identify the objects generating more redo. Unfortunately, redo size is not tracked at a segment level. However, you can make an educated guess using ‘db block changes’ statistics. But, you must use logminer utility to identify the objects generating more redo scientifically.
Detecting redo size increase
AWR tables (require Diagnostics license) can be accessed to identify the redo size increase. Following query spools the daily rate of redo size. You can easily open the output file redosize.lst in an Excel spreadsheet and graph the data to visualize the redo size change. Use pipe symbol as the delimiter while opening the file in excel spreadsheet.
The restart of a UNIX server call initialization scripts to start processes and daemons. Every platform has a unique directory structure and follows a method to implement server startup sequence. In Linux platform (prior to Linux 6), initialization scripts are started by calling scripts in the /etc/rcX.d directories, where X denotes the run level of the UNIX server. Typically, Clusterware is started at run level 3. For example, ohasd daemon started by /etc/rc3.d/S96ohasd file by supplying start as an argument. File S96ohasd is linked to /etc/init.d/ohasd.
S96ohasd -> /etc/init.d/ohasd /etc/rc3.d/S96ohasd start # init daemon starting ohasd.
Similarly, a server shutdown will call scripts in rcX.d directories, for example, ohasd is shut down by calling K15ohasd script:
I’ve recently realized that I didn’t post anywhere the second version of my presentation — Under The Hood of Oracle Clusterware 2.0: Grid Infrastructure, codenamed UTHOC2. I think it would be very useful as I still see lots of questions being asked and UTHOC1 covers Oracle RAC 10g and 11gR1 only. 11g Release 2 brought many changes in the clusterware and the slides needed some good refresh.
I’ve purposely left it as an 220.127.116.11 installation as you can get this from OTN without needing access to My Oracle Support (MOS). The process works just as well for 18.104.22.168 and I would recommend you use that if you do have access to MOS. Remember, if you are doing the RAC installation on Oracle Linux 6 you are going to need 22.214.171.124, so OL5 might be the right option if you are playing around with this at home with no access to MOS.
I spent today updating my Oracle 11gR2 RAC installation on OL6 article. The original article used an older version of VirtualBox , which meant some of the screen shots looked a little dated. It’s now updated to VirtualBox 4.2.6, so it should be a little less confusing for anyone who is new to VirtualBox.
I’ll probably update the OL5 RAC article some time this next week, since that article uses VirtualBox 3.2.8, which is pretty much ancient history now.
Followers of my blog know I like doing virtual RAC installations.When I do these I’m focusing very much on the Oracle side of things, leaving the virtualization tool to handle the hardware virtualization, like networking and shared disk.
A few weeks ago Gilbert Standen contacted me to say he had done a virtual RAC installation using OpenvSwitch to virtualize the network components. He posted some basic tips here. When I mentioned it on G+ and twitter, it generated some interest, so I suggested he write it up with a little more detail. That process has started now on his blog. You can see the first couple of articles here:
There are many questions from few of my clients about asmlib support in RHEL6, as they are gearing up to upgrade the database servers to RHEL6. There is a controversy about asmlib support in RHEL6. As usual, I will only discuss technical details in this blog entry.
ASMLIB is applicable only to Linux platform and does not apply to any other platform.
Now, you might ask why bother and why not just use OEL and UK? Well, not every Linux server is used as a database server. In a typical company, there are hundreds of Linux servers and just few percent of those servers are used as Database servers. Linux system administrators prefer to keep one flavor of Linux distribution for management ease and so, asking clients to change the distribution from RHEL to OEL or OEL to RHEL is always not a viable option.
Do you need to use ASMLIB in Linux?
This is a quick note about reverse path filtering and impact of that feature to RAC. I encountered an interesting problem recently with a client and it is worth blogging about it, with a strong hope that it might help one of you in the future.
Environment is 126.96.36.199 GI, Linux 5.6. In a 3 node cluster, Grid Infrastructure (GI) comes up cleanly in just one node, but never comes up in other nodes. If we shutdown GI in first node, we can start the GI in second node with no issues. Meaning, GI can be up in just one node at any time.
System Admins indicated that there are no major changes, only few bug fixes. Seemingly, problem started after those bug fixes. But there were few other changes to the environment /init.ora parameter change etc. So, the problem was not immediately attributable to just OS changes.
Let’s first discuss how RAC traffic works before continuing. Environment for the discussion is: 2 node cluster with 8K database block size, UDP protocol is used for cache fusion. (BTW, UDP and RDS protocols are supported in UNIX platform; whereas Windows uses TCP protocol).
UDP protocol, fragmentation, and assembly
UDP Protocol is an higher level protocol stack, and it is implemented over IP Protocol ( UDP/IP). Cache Fusion uses UDP protocol to send packets over the wire (Exadata uses RDS protocol though).